Nontranscribed spacers in Drosophila ribosomal DNA (original) (raw)
Related papers
X and Y chromosomal ribosomal DNA of drosophila: comparison of spacers and insertions
Cell, 1978
In Drosophila melanogaster, the genes coding for 18s and 28s ribosomal RNA (rDNA) are clustered at one locus each on the X and the Y chromosomes. We have compared the structure of rDNA at the two loci. The 18s and 28s rRNAs coded by the X and Y chromosomes are very similar and probably identical (Maden and Tartof, 1974). In D. melanogaster, many rDNA repeating units are interrupted in the 28s RNA sequence by a DNA region called the insertion. There are at least two sequence types of insertions. Type 1 insertions include the most abundant 5 kilobase (kb) class and homologous small (0.5 and 1 kb) insertions. Most insertions between 1.5 and 4 kb have no homology to the 5 kb class and are identified as type 2 insertions. In X rDNA, about 49% of all rDNA repeats have type 1 insertions, and another 16% have type 2 insertions. On the Y chromosome, only 16% of all rDNA repeats are interrupted, and most if not all insertions are of type 2. rDNA fragments derived from the X and Y chromosomes have been cloned in E. coli. The homology between the nontranscribed spacers in X and Y rDNA was studied with cloned fragments. Stable heteroduplexes were found which showed that these regions on the two chromosomes are very similar. The evolution of rDNA in D. melanogaster might involve genetic exchange between the X and Y chromosomal clusters with restrictions on the movement of type 1 insertions to the Y chromosome.
Characterization of ribosomal DNA (rDNA) in Drosophila arizonae
Genetics and Molecular Biology, 2000
Ribosomal DNA (rDNA) is a multigenic family composed of one or more clusters of repeating units (RU). Each unit consists of highly conserved sequences codifying 18S, 5.8S and 28S rRNA genes intercalated with poorly conserved regulatory sequences between species. In this work, we analyzed the rDNA of Drosophila arizonae, a member of the mulleri complex (Repleta group). Using genomic restriction patterns, cloning and mapping of some representative rDNA fragments, we were able to construct a representative restriction map. RU in this species are 13.5-14 kb long, restriction sites are completely conserved compared with other drosophilids and the rDNA has an R1 retrotransposable element in some RU. We were unable to detect R2 elements in this species.
Characterization of cloned ribosomal DNA from Drosophila hydei
Nucleic Acids Research, 1980
The structure of ribosomal genes from the fly Drosophila hydei has been analyzed. EcoRI fragments, cloned in a plasmid vector, were mapped by restriction enzyme analysis. The lengths of the regions coding for 18S and 28S rRNA were defined by Rloop formation. From these data a physical map of the rRNA genes was constructed. There are two major types of rDNA units in D. hydei, one having a size of 11 kb and the other a size of 17 kb. The 17 kb unit results from an intervening sequence (ivs) of 6.0 kb, interrupting the a-28S rRNA coding region. Some homology between the D. hydei ivs and D. melanogaster type 1 ivs has been described previously (1). However, the restriction sites within these ivs show considerable divergence. Whereas D. hydei rDNA sequences coding for mature rRNAs share restriction sites with D. melanogaster rDNA, the nontranscribed spacer has little, if any, sequence homology. Despite difference in sequence, D. hydei and D. melanogaster spacers show structural similarities in that both contain repeated sequence elements of similar size and location.
Complete Sequences of the rRNA Genes of Drosophila melanogaster 1
Molecular Biology and Evolution, 1988
In this, the first of three papers, we present the sequence of the ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of D. melanogaster rDNA encode four individual rRNAs: 18s (1,995 nt), 5.8s (123 nt), 2s (30 nt), and 28s (3,945 nt). The ribosomal DNA (rDNA) repeat of D. melanogaster is AT rich (65.9% overall), with the spacers being particularly AT rich. Analysis of DNA simplicity reveals that, in contrast to the intergenic spacer (IGS) and the external transcribed spacer (ETS), most of the rRNA gene regions have been refractory to the action of slippage-like events, with the exception of the 28s rRNA gene expansion segments. It would seem that the 28s rRNA can accommodate the products of slippage-like events without loss of activity. In the following two papers we analyze the effects of sequence divergence on the evolution of (1) the 28s gene "expansion segments" and (2) the 28s and 18s rRNA secondary structures among eukaryotic species, respectively. Our detailed analyses reveal, in addition to unequal crossingover, (1) the involvement of slippage and biased mutation in the evolution of the rDNA multigene family and (2) the molecular coevolution of both expansion segments and the nucleotides involved with compensatory changes required to maintain secondary structures of RNA.
Complete sequences of the rRNA genes of Drosophila melanogaster
Molecular biology and evolution, 1988
In this, the first of three papers, we present the sequence of the ribosomal RNA (rRNA) genes of Drosophila melanogaster. The gene regions of D. melanogaster rDNA encode four individual rRNAs: 18S (1,995 nt), 5.8S (123 nt), 2S (30 nt), and 28S (3,945 nt). The ribosomal DNA (rDNA) repeat of D. melanogaster is AT rich (65.9% overall), with the spacers being particularly AT rich. Analysis of DNA simplicity reveals that, in contrast to the intergenic spacer (IGS) and the external transcribed spacer (ETS), most of the rRNA gene regions have been refractory to the action of slippage-like events, with the exception of the 28S rRNA gene expansion segments. It would seem that the 28S rRNA can accommodate the products of slippage-like events without loss of activity. In the following two papers we analyze the effects of sequence divergence on the evolution of (1) the 28S gene "expansion segments" and (2) the 28S and 18S rRNA secondary structures among eukaryotic species, respectivel...
Cloned segment of Drosophila melanogaster rDNA containing new types of sequence insertion
Proceedings of the National Academy of Sciences, 1977
A cloned 14.3-kbase segment of Drosophila melanogaster rDNA (Dm207) is described in which only a 4-kbase region is homologous to a cloned 17-kbase rDNA repeating unit, Dm103; this 4-kbase region consists of part of the 28S rRNA gene and most but not all of the adjacent transcribed spacer that normally connects the 18S and 28S genes. The transcribed spacer in Dm207 is interrupted by a 2.2-kbase stretch of DNA that does not contain any 18S gene sequences. At the other end of the 4-kbase homology, the 28S gene is interrupted by an 8.1-kbase stretch of DNA at a position equivalent to the site of the 28S insertion found in the 17-kbase units. The question of whether the 2.2-kbase and 8.1-kbase interrupter segments in Dm207 derive from longer insertions into the transcribed spacer and 28S genes of a very long repeating unit (greater than or equal to 22 kbases) or represent a region of the chromosomal DNA into which a 4-kbase fragment of rDNA has been inserted is discussed.
The Ribosomes of Drosophila. III. Rna and Protein Homology Between D. Melanogaster and D. Virilis
Genetics, 1976
T i e extent of interspecific homology between D. melanogaster and D. virilis for ribosomal RNA and ribosomal protein was examined using the techniques of two-dimensional gel electrophoresis, and RNA-DNA filter hybridization. Only 2 of the 71 ribosomal proteins resolved were found to be species specific, while comparisons of soluble larval hemolymph protein patterns showed little similarity. Depending on the technique employed, the sequence homology for 18s + 28s ribosomal RNA was found to be between 83-94%, and sequence homology for 5s rRNA was judged to be complete.
Heredity, 2005
The evolution of the chromosomal location of ribosomal RNA gene clusters and the organization of heterochromatin in the Drosophila melanogaster group were investigated using fluorescence in situ hybridization and DAPI staining to mitotic chromosomes. The investigation of 18 species (11 of which were being examined for the first time) belonging to the melanogaster and ananassae subgroups suggests that the ancestral configuration consists of one nucleolus organizer (NOR) on each sex chromosome. This pattern, which is conserved throughout the melanogaster subgroup, except in D. simulans and D. sechellia, was observed only in the ercepeae complex within the ananassae subgroup. Both sexlinked NORs must have been lost in the lineage leading to D. varians and in the ananassae and bipectinata complexes, whereas new sites, characterized by intra-species variation in hybridization signal size, appeared on the fourth chromosome related to heterochromatic rearrangements. Nucleolar material is thought to be required for sex chromosome pairing and disjunction in a variety of organisms including Drosophila. Thus, either remnant sequences, possibly intergenic spacer repeats, are still present in the sex chromosomes which have lost their NORs (as observed in D. simulans and D. sechellia), or an alternative mechanism has evolved. Heredity (2005) 94, 388-395.