Gregory Copenhaver | University of North Carolina at Chapel Hill (original) (raw)

Papers by Gregory Copenhaver

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2014

During meiosis homologous chromosomes undergo crossover recombination. Sequence differences betwe... more During meiosis homologous chromosomes undergo crossover recombination. Sequence differences between homologs can locally inhibit crossovers. Despite this, nucleotide diversity and population-scaled recombination are positively correlated in eukaryote genomes. To investigate interactions between heterozygosity and recombination we crossed Arabidopsis lines carrying fluorescent crossover reporters to 32 diverse accessions and observed hybrids with significantly higher and lower crossovers than homozygotes. Using recombinant populations derived from these crosses we observed that heterozygous regions increase crossovers when juxtaposed with homozygous regions, which reciprocally decrease. Total crossovers measured by chiasmata were unchanged when heterozygosity was varied, consistent with homeostatic control. We tested the effects of heterozygosity in mutants where the balance of interfering and non-interfering crossover repair is altered. Crossover remodeling at homozygosity-heterozygosity junctions requires interference, and non-interfering repair is inefficient in heterozygous regions. As a consequence, heterozygous regions show stronger crossover interference. Our findings reveal how varying homolog polymorphism patterns can shape meiotic recombination.

PLOS Genetics, Dec 20, 2018

PLOS Genetics, Sep 13, 2018

One of the most rewarding aspects of serving as an editor is the opportunity to see, appreciate, ... more One of the most rewarding aspects of serving as an editor is the opportunity to see, appreciate, and celebrate great science from our authors. With this motivation in mind, the annual PLOS Genetics Research Prize was established several years ago to recognize a paper published in the previous 12 months that was scientifically excellent and had broad impact across the genetics community. Nominations are open to the public, and the winner is selected by the PLOS Genetics Editors-in-Chief and Section Editors. This year, there were a number of very strong nominations. Besides the prize recipient described further below, there are two additional papers that are especially notable. An article by Amelie Baud and colleagues demonstrates that over 100 diverse phenotypes in mice are affected by social interactions [1]. This work was fascinating because it examines a relatively under-studied phenomenon that has far-reaching implications for genetic analyses. It also received broad attention with coverage in over 39 media reports and blogs. Another article by Carlos Eduardo Amorim and colleagues examined the long-standing quandary of why lethal alleles persist in human populations, and comes to the surprising conclusion that ascertainment bias is a significant contributing factor [2]. This work was also broadly impactful and widely discussed on social media. This year's prize recipient is an article by Timothy Mullen and Sarah Wignall [3], striking in many ways, not the least of which was that it was nominated independently by four different members of the genetics community. In what follows, these nominators tell us more about the significance and impact of the work. During chromosome segregation, the spindle is assembled from microtubules to accurately partition chromosomes. In most systems, spindle assembly initiates from centriole-containing centrosomes, generating a highly organized, polarized array of microtubules capable of pulling chromosomes to opposite poles [4]. However, female reproductive cells (oocytes) in many species, including humans, segregate chromosomes on acentriolar spindles assembled through unique mechanisms. Acentriolar spindles are frequently associated with aberrant chromosome

PLOS Genetics, Oct 29, 2020

PLOS Genetics, Oct 11, 2019

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2009

During meiosis, chromatin undergoes extensive changes to facilitate recombination, homolog pairin... more During meiosis, chromatin undergoes extensive changes to facilitate recombination, homolog pairing, and chromosome segregation. To investigate the relationship between chromatin organization and meiotic processes, we used formaldehydeassisted isolation of regulatory elements (FAIRE) to map open chromatin during the transition from mitosis to meiosis in the budding yeast Saccharomyces cerevisiae. We found that meiosis-induced opening of chromatin is associated with meiotic DSB hotpots. The positive association between open chromatin and DSB hotspots is most prominent 3 h into meiosis, when the early meiotic genes DMC1 and HOP1 exhibit maximum transcription and the early recombination genes SPO11 and RAD51 are strongly up-regulated. While the degree of chromatin openness is positively associated with the occurrence of recombination hotspots, many hotspots occur outside of open chromatin. Of particular interest, many DSB hotspots that fell outside of meiotic open chromatin nonetheless occurred in chromatin that had recently been open during mitotic growth. Finally, we find evidence for meiosis-specific opening of chromatin at the regions adjacent to boundaries of subtelomeric sequences, which exhibit specific crossover control patterns hypothesized to be regulated by chromatin.

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2007

Recombination, in the form of cross-overs (COs) and gene conversion (GC), is a highly conserved f... more Recombination, in the form of cross-overs (COs) and gene conversion (GC), is a highly conserved feature of meiosis from fungi to mammals. Recombination helps ensure chromosome segregation and promotes allelic diversity. Lesions in the recombination machinery are often catastrophic for meiosis, resulting in sterility. We have developed a visual assay capable of detecting Cos and GCs and measuring CO interference in Arabidopsis thaliana. This flexible assay utilizes transgene constructs encoding pollen-expressed fluorescent proteins of three different colors in the qrt1 mutant background. By observing the segregation of the fluorescent alleles in 92,489 pollen tetrads, we demonstrate (i) a correlation between developmental position and CO frequency, (ii) a temperature dependence for CO frequency, (iii) the ability to detect meiotic GC events, and (iv) the ability to rapidly assess CO interference. cross-over ͉ meiosis ͉ tetrad ͉ gene conversion ͉ interference

PLOS Genetics, Dec 1, 2016

Plant Journal, Feb 1, 1996

Ribosomal RNA genes are organized in tandem arrays called nucleolus organizer regions (NORs). In ... more Ribosomal RNA genes are organized in tandem arrays called nucleolus organizer regions (NORs). In a prior study, RFLP mapping on pulsed-field gels placed NOR2 at the northern tip of Arabidopsis thaliana chromosome 2. New polymorphisms have allowed the other NOR, NOR4, to be mapped to the northern tip of chromosome 4. To map NOR-associated loci, rDNA-specific cleavage by I-Ppol, an endonuclease with a 15 nucleotide recognition sequence involved in rDNA-homing of a mobile, self-splicing Group I intron in Physarum was exploited. I-Ppol digestion of A. thaliana genomic DNA liberated two telomere-containing fragments no larger than 13 kbp, and telomere polymorphisms identified using I-Ppol cosegregated with NOR2 and NOR4. Restriction mapping suggested that telomere-proximal rRNA genes are oriented with their 5' ends nearest the chromosome ends and their 3' ends nearest the centromere. This orientation was confirmed using the polymerase chain reaction to clone one of the telomere-rDNA junctions, most likely the junction on chromosome 4. The telomeric repeats join the terminal rRNA gene downstream of its promoter, suggesting that this first gene is inactive. Subtelomeric repetitive DNAs are absent at the telomere-rDNA junction. Localization of NOR2, NOR4 and their associated telomeres, TEL2N and TEL4N, respectively, provides end points for the genetic and physical maps of chromosomes 2 and 4.

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2023

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2006

Arabidopsis (Arabidopsis thaliana) QUARTET (QRT) genes are required for pollen separation during ... more Arabidopsis (Arabidopsis thaliana) QUARTET (QRT) genes are required for pollen separation during normal floral development. In qrt mutants, the four products of microsporogenesis remain fused and pollen grains are released as tetrads. In Arabidopsis, tetrad analysis in qrt mutants has been used to map all five centromeres, easily distinguish sporophytic from gametophytic mutations, and accurately assess crossover interference. Using a combination of forward and reverse genetics, we have identified the gene responsible for the qrt1 phenotype. Annotation predicts that QRT1 encodes a pectin methylesterase (PME), and enzymatic assays of QRT1 expressed in Escherichia coli indicate that QRT1 has PME activity. Promoter and transcription analysis demonstrate QRT1 is expressed in anther tissues shortly after meiosis is complete. Unexpectedly, the QRT1 promoter is also active in a variety of developmentally unrelated tissues, including developing guard cells, the hypocotyl-root transition zone, areas of lateral root emergence, and floral nectaries. PMEs constitute a large gene family in Arabidopsis, are involved in cell wall loosening, and have been implicated in various aspects of floral development and pollen tube elongation. The identification of QRT1 as a PME contributes to our understanding of pollen development and may help to provide valuable genetic tools in other plant species.

New Phytologist, Sep 18, 2015

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2015

Cell division requires proper spindle assembly; a surveillance pathway, the spindle assembly chec... more Cell division requires proper spindle assembly; a surveillance pathway, the spindle assembly checkpoint (SAC), monitors whether the spindle is normal and correctly attached to kinetochores. The SAC proteins regulate mitotic chromosome segregation by affecting CDC20 (Cell Division Cycle 20) function. However, it is unclear whether CDC20 regulates meiotic spindle assembly and proper homolog segregation. Here, we show that the Arabidopsis thaliana CDC20.1 gene is indispensable for meiosis and male fertility. We demonstrate that cdc20.1 meiotic chromosomes align asynchronously and segregate unequally and the metaphase I spindle has aberrant morphology. Comparison of the distribution of meiotic stages at different time points between the wild type and cdc20.1 reveals a delay of meiotic progression from diakinesis to anaphase I. Furthermore, cdc20.1 meiocytes exhibit an abnormal distribution of a histone H3 phosphorylation mark mediated by the Aurora kinase, providing evidence that CDC20.1 regulates Aurora localization for meiotic chromosome segregation. Further evidence that CDC20.1 and Aurora are functionally related was provided by meiosis-specific knockdown of At-Aurora1 expression, resulting in meiotic chromosome segregation defects similar to those of cdc20.1. Taken together, these results suggest a critical role for CDC20.1 in SAC-dependent meiotic chromosome segregation.

Frontiers in Plant Science, Mar 9, 2021

Plants, like all sexually reproducing organisms, create genetic variability by reshuffling parent... more Plants, like all sexually reproducing organisms, create genetic variability by reshuffling parental alleles during meiosis. Patterns of genetic variation in the resulting gametes are determined by the independent assortment of chromosomes in meiosis I and by the number and positioning of crossover (CO) events during meiotic recombination. On the chromosome level, spatial distribution of CO events is biased by multiple regulatory mechanisms, such as CO assurance, interference and homeostasis. However, little is known about how multiple COs are distributed among the four chromatids of a bivalent. Chromatid interference (CI) has been proposed as a regulatory mechanism that biases distribution of multiple COs toward specific chromatid partners, however, its existence has not been well-studied and its putative mechanistic basis remains undescribed. Here, we introduce a novel method to quantitatively express CI, and take advantage of available tetrad-based genotyping data from Arabidopsis and maize male meiosis to quantify CI effects on a genome-wide and chromosomal scale. Overall, our analyses reveal random involvement of sister chromatids in double CO events across paired chromosomes, indicating an absence of CI. However, on a genome-wide level, CI was found to vary with physical distance between COs, albeit with different effects in Arabidopsis and maize. While effects of CI are minor in Arabidopsis and maize, the novel methodology introduced here enables quantitative interpretation of CI both on a local and genome-wide scale, and thus provides a key tool to study CI with relevance for both plant genetics and crop breeding.

Current Biology, Apr 1, 2005

Molecular and Cellular Biology, Oct 1, 1994

Nucleic Acids Research, 1994

Upstream Binding Factor (UBF) is important for activation of ribosomal RNA transcription and belo... more Upstream Binding Factor (UBF) is important for activation of ribosomal RNA transcription and belongs to a family of proteins containing nucleic acid binding domains, termed HMG-boxes, with similarity to High Mobility Group (HMG) chromosomal proteins. Proteins in this family can be sequence-specific or highly sequence-tolerant binding proteins. We show that Xenopus UBF can be classified among the sequencetolerant class. Methylation interference assays using enhancer DNA probes failed to reveal any critical nucleotides required for UBF binding. Selection by UBF of optimal binding sites among a population of enhancer oligonucleotides with randomized sequences also failed to reveal any consensus sequence. The minor groove specific drugs chromomycin A3, distamycin A and actinomycin D competed against UBF for enhancer binding, suggesting that UBF, like other HMG-box proteins, probably interacts with the minor groove. UBF also shares with other HMG box proteins the ability to bind synthetic cruciform DNA. However, UBF appears different from other HMG-box proteins in that it can bind both RNA (tRNA) and DNA. The sequence-tolerant nature of UBFnucleic acid interactions may accommodate the rapid evolution of ribosomal RNA gene sequences.

Nature Biotechnology, May 1, 2010

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Nov 25, 2008

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2014

During meiosis homologous chromosomes undergo crossover recombination. Sequence differences betwe... more During meiosis homologous chromosomes undergo crossover recombination. Sequence differences between homologs can locally inhibit crossovers. Despite this, nucleotide diversity and population-scaled recombination are positively correlated in eukaryote genomes. To investigate interactions between heterozygosity and recombination we crossed Arabidopsis lines carrying fluorescent crossover reporters to 32 diverse accessions and observed hybrids with significantly higher and lower crossovers than homozygotes. Using recombinant populations derived from these crosses we observed that heterozygous regions increase crossovers when juxtaposed with homozygous regions, which reciprocally decrease. Total crossovers measured by chiasmata were unchanged when heterozygosity was varied, consistent with homeostatic control. We tested the effects of heterozygosity in mutants where the balance of interfering and non-interfering crossover repair is altered. Crossover remodeling at homozygosity-heterozygosity junctions requires interference, and non-interfering repair is inefficient in heterozygous regions. As a consequence, heterozygous regions show stronger crossover interference. Our findings reveal how varying homolog polymorphism patterns can shape meiotic recombination.

PLOS Genetics, Dec 20, 2018

PLOS Genetics, Sep 13, 2018

One of the most rewarding aspects of serving as an editor is the opportunity to see, appreciate, ... more One of the most rewarding aspects of serving as an editor is the opportunity to see, appreciate, and celebrate great science from our authors. With this motivation in mind, the annual PLOS Genetics Research Prize was established several years ago to recognize a paper published in the previous 12 months that was scientifically excellent and had broad impact across the genetics community. Nominations are open to the public, and the winner is selected by the PLOS Genetics Editors-in-Chief and Section Editors. This year, there were a number of very strong nominations. Besides the prize recipient described further below, there are two additional papers that are especially notable. An article by Amelie Baud and colleagues demonstrates that over 100 diverse phenotypes in mice are affected by social interactions [1]. This work was fascinating because it examines a relatively under-studied phenomenon that has far-reaching implications for genetic analyses. It also received broad attention with coverage in over 39 media reports and blogs. Another article by Carlos Eduardo Amorim and colleagues examined the long-standing quandary of why lethal alleles persist in human populations, and comes to the surprising conclusion that ascertainment bias is a significant contributing factor [2]. This work was also broadly impactful and widely discussed on social media. This year's prize recipient is an article by Timothy Mullen and Sarah Wignall [3], striking in many ways, not the least of which was that it was nominated independently by four different members of the genetics community. In what follows, these nominators tell us more about the significance and impact of the work. During chromosome segregation, the spindle is assembled from microtubules to accurately partition chromosomes. In most systems, spindle assembly initiates from centriole-containing centrosomes, generating a highly organized, polarized array of microtubules capable of pulling chromosomes to opposite poles [4]. However, female reproductive cells (oocytes) in many species, including humans, segregate chromosomes on acentriolar spindles assembled through unique mechanisms. Acentriolar spindles are frequently associated with aberrant chromosome

PLOS Genetics, Oct 29, 2020

PLOS Genetics, Oct 11, 2019

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2009

During meiosis, chromatin undergoes extensive changes to facilitate recombination, homolog pairin... more During meiosis, chromatin undergoes extensive changes to facilitate recombination, homolog pairing, and chromosome segregation. To investigate the relationship between chromatin organization and meiotic processes, we used formaldehydeassisted isolation of regulatory elements (FAIRE) to map open chromatin during the transition from mitosis to meiosis in the budding yeast Saccharomyces cerevisiae. We found that meiosis-induced opening of chromatin is associated with meiotic DSB hotpots. The positive association between open chromatin and DSB hotspots is most prominent 3 h into meiosis, when the early meiotic genes DMC1 and HOP1 exhibit maximum transcription and the early recombination genes SPO11 and RAD51 are strongly up-regulated. While the degree of chromatin openness is positively associated with the occurrence of recombination hotspots, many hotspots occur outside of open chromatin. Of particular interest, many DSB hotspots that fell outside of meiotic open chromatin nonetheless occurred in chromatin that had recently been open during mitotic growth. Finally, we find evidence for meiosis-specific opening of chromatin at the regions adjacent to boundaries of subtelomeric sequences, which exhibit specific crossover control patterns hypothesized to be regulated by chromatin.

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2007

Recombination, in the form of cross-overs (COs) and gene conversion (GC), is a highly conserved f... more Recombination, in the form of cross-overs (COs) and gene conversion (GC), is a highly conserved feature of meiosis from fungi to mammals. Recombination helps ensure chromosome segregation and promotes allelic diversity. Lesions in the recombination machinery are often catastrophic for meiosis, resulting in sterility. We have developed a visual assay capable of detecting Cos and GCs and measuring CO interference in Arabidopsis thaliana. This flexible assay utilizes transgene constructs encoding pollen-expressed fluorescent proteins of three different colors in the qrt1 mutant background. By observing the segregation of the fluorescent alleles in 92,489 pollen tetrads, we demonstrate (i) a correlation between developmental position and CO frequency, (ii) a temperature dependence for CO frequency, (iii) the ability to detect meiotic GC events, and (iv) the ability to rapidly assess CO interference. cross-over ͉ meiosis ͉ tetrad ͉ gene conversion ͉ interference

PLOS Genetics, Dec 1, 2016

Plant Journal, Feb 1, 1996

Ribosomal RNA genes are organized in tandem arrays called nucleolus organizer regions (NORs). In ... more Ribosomal RNA genes are organized in tandem arrays called nucleolus organizer regions (NORs). In a prior study, RFLP mapping on pulsed-field gels placed NOR2 at the northern tip of Arabidopsis thaliana chromosome 2. New polymorphisms have allowed the other NOR, NOR4, to be mapped to the northern tip of chromosome 4. To map NOR-associated loci, rDNA-specific cleavage by I-Ppol, an endonuclease with a 15 nucleotide recognition sequence involved in rDNA-homing of a mobile, self-splicing Group I intron in Physarum was exploited. I-Ppol digestion of A. thaliana genomic DNA liberated two telomere-containing fragments no larger than 13 kbp, and telomere polymorphisms identified using I-Ppol cosegregated with NOR2 and NOR4. Restriction mapping suggested that telomere-proximal rRNA genes are oriented with their 5' ends nearest the chromosome ends and their 3' ends nearest the centromere. This orientation was confirmed using the polymerase chain reaction to clone one of the telomere-rDNA junctions, most likely the junction on chromosome 4. The telomeric repeats join the terminal rRNA gene downstream of its promoter, suggesting that this first gene is inactive. Subtelomeric repetitive DNAs are absent at the telomere-rDNA junction. Localization of NOR2, NOR4 and their associated telomeres, TEL2N and TEL4N, respectively, provides end points for the genetic and physical maps of chromosomes 2 and 4.

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2023

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2006

Arabidopsis (Arabidopsis thaliana) QUARTET (QRT) genes are required for pollen separation during ... more Arabidopsis (Arabidopsis thaliana) QUARTET (QRT) genes are required for pollen separation during normal floral development. In qrt mutants, the four products of microsporogenesis remain fused and pollen grains are released as tetrads. In Arabidopsis, tetrad analysis in qrt mutants has been used to map all five centromeres, easily distinguish sporophytic from gametophytic mutations, and accurately assess crossover interference. Using a combination of forward and reverse genetics, we have identified the gene responsible for the qrt1 phenotype. Annotation predicts that QRT1 encodes a pectin methylesterase (PME), and enzymatic assays of QRT1 expressed in Escherichia coli indicate that QRT1 has PME activity. Promoter and transcription analysis demonstrate QRT1 is expressed in anther tissues shortly after meiosis is complete. Unexpectedly, the QRT1 promoter is also active in a variety of developmentally unrelated tissues, including developing guard cells, the hypocotyl-root transition zone, areas of lateral root emergence, and floral nectaries. PMEs constitute a large gene family in Arabidopsis, are involved in cell wall loosening, and have been implicated in various aspects of floral development and pollen tube elongation. The identification of QRT1 as a PME contributes to our understanding of pollen development and may help to provide valuable genetic tools in other plant species.

New Phytologist, Sep 18, 2015

Carolina Digital Repository (University of North Carolina at Chapel Hill), 2015

Cell division requires proper spindle assembly; a surveillance pathway, the spindle assembly chec... more Cell division requires proper spindle assembly; a surveillance pathway, the spindle assembly checkpoint (SAC), monitors whether the spindle is normal and correctly attached to kinetochores. The SAC proteins regulate mitotic chromosome segregation by affecting CDC20 (Cell Division Cycle 20) function. However, it is unclear whether CDC20 regulates meiotic spindle assembly and proper homolog segregation. Here, we show that the Arabidopsis thaliana CDC20.1 gene is indispensable for meiosis and male fertility. We demonstrate that cdc20.1 meiotic chromosomes align asynchronously and segregate unequally and the metaphase I spindle has aberrant morphology. Comparison of the distribution of meiotic stages at different time points between the wild type and cdc20.1 reveals a delay of meiotic progression from diakinesis to anaphase I. Furthermore, cdc20.1 meiocytes exhibit an abnormal distribution of a histone H3 phosphorylation mark mediated by the Aurora kinase, providing evidence that CDC20.1 regulates Aurora localization for meiotic chromosome segregation. Further evidence that CDC20.1 and Aurora are functionally related was provided by meiosis-specific knockdown of At-Aurora1 expression, resulting in meiotic chromosome segregation defects similar to those of cdc20.1. Taken together, these results suggest a critical role for CDC20.1 in SAC-dependent meiotic chromosome segregation.

Frontiers in Plant Science, Mar 9, 2021

Plants, like all sexually reproducing organisms, create genetic variability by reshuffling parent... more Plants, like all sexually reproducing organisms, create genetic variability by reshuffling parental alleles during meiosis. Patterns of genetic variation in the resulting gametes are determined by the independent assortment of chromosomes in meiosis I and by the number and positioning of crossover (CO) events during meiotic recombination. On the chromosome level, spatial distribution of CO events is biased by multiple regulatory mechanisms, such as CO assurance, interference and homeostasis. However, little is known about how multiple COs are distributed among the four chromatids of a bivalent. Chromatid interference (CI) has been proposed as a regulatory mechanism that biases distribution of multiple COs toward specific chromatid partners, however, its existence has not been well-studied and its putative mechanistic basis remains undescribed. Here, we introduce a novel method to quantitatively express CI, and take advantage of available tetrad-based genotyping data from Arabidopsis and maize male meiosis to quantify CI effects on a genome-wide and chromosomal scale. Overall, our analyses reveal random involvement of sister chromatids in double CO events across paired chromosomes, indicating an absence of CI. However, on a genome-wide level, CI was found to vary with physical distance between COs, albeit with different effects in Arabidopsis and maize. While effects of CI are minor in Arabidopsis and maize, the novel methodology introduced here enables quantitative interpretation of CI both on a local and genome-wide scale, and thus provides a key tool to study CI with relevance for both plant genetics and crop breeding.

Current Biology, Apr 1, 2005

Molecular and Cellular Biology, Oct 1, 1994

Nucleic Acids Research, 1994

Upstream Binding Factor (UBF) is important for activation of ribosomal RNA transcription and belo... more Upstream Binding Factor (UBF) is important for activation of ribosomal RNA transcription and belongs to a family of proteins containing nucleic acid binding domains, termed HMG-boxes, with similarity to High Mobility Group (HMG) chromosomal proteins. Proteins in this family can be sequence-specific or highly sequence-tolerant binding proteins. We show that Xenopus UBF can be classified among the sequencetolerant class. Methylation interference assays using enhancer DNA probes failed to reveal any critical nucleotides required for UBF binding. Selection by UBF of optimal binding sites among a population of enhancer oligonucleotides with randomized sequences also failed to reveal any consensus sequence. The minor groove specific drugs chromomycin A3, distamycin A and actinomycin D competed against UBF for enhancer binding, suggesting that UBF, like other HMG-box proteins, probably interacts with the minor groove. UBF also shares with other HMG box proteins the ability to bind synthetic cruciform DNA. However, UBF appears different from other HMG-box proteins in that it can bind both RNA (tRNA) and DNA. The sequence-tolerant nature of UBFnucleic acid interactions may accommodate the rapid evolution of ribosomal RNA gene sequences.

Nature Biotechnology, May 1, 2010

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Nov 25, 2008