Authentic reverse transcriptase is coded by jockey, a mobile Drosophila element related to mammalian LINEs (original) (raw)
Related papers
[Analysis of the suffix short retroelement copies and the encoded protein domain of Drosophila]
Genetika, 2002
To analyze the copies of the suffix short retro-element, its homologs were sought in nucleic acid sequence databases of the Drosophila melanogaster genome. The search yielded several conserved (near identical in sequence) copies, which are indicative of recent suffix transposition, and numerous divergent copies, which suggest ancient suffix transposition. Analysis of the short suffix ORF revealed a conserved protein domain, which was also found as the eighth C-terminal domain in reverse transcriptases of certain long interspersed elements (LINEs). The suffix-encoded polypeptide proved to be homologous to DNA- and RNA-recognizing domains.
Insect Biochemistry and Molecular Biology, 2005
ZAM is an LTR-retrotransposon from Drosophila melanogaster that belongs to the genus errantivirus, viruses similar in structure and replication cycle to vertebrate retroviruses. A key component to its lifecycle is its reverse transcriptase which copies singlestranded genomic RNA into DNA. Here, we provide a detailed characterization of the enzymatic activities of the reverse transcriptase encoded by ZAM. When expressed in vitro, the reverse transcriptase domain associated with the RNase H domain encoded by the ZAM pol gene forms homodimers and displays an efficient RNA-dependent DNA-polymerase activity. It requires either Mg 2+ or Mn 2+ divalent cations, and works in basic pH, with a peak at around pH9. The so-called [RT-RH] polypeptide displays an optimal activity at 22 1C, a property that makes it well-adapted to the temperature of its host. This study contributes to our understanding of the general structures and functions of retroviral reverse transcriptases, a necessary process in the search for novel inhibitors. r
PLoS ONE, 2011
Transposition of two retroelements (Ulysses and Penelope) mobilized in the course of hybrid dysgenesis in Drosophila virilis has been investigated by in situ hybridization on polytene chromosomes in two D. virilis strains of different cytotypes routinely used to get dysgenic progeny. The analysis has been repeatedly performed over the last two decades, and has revealed transpositions of Penelope in one of the strains, while, in the other strain, the LTR-containing element Ulysses was found to be transpositionally active. The gypsy retroelement, which has been previously shown to be transpositionally inactive in D. virilis strains, was also included in the analysis. Whole mount is situ hybridization with the ovaries revealed different subcellular distribution of the transposable elements transcripts in the strains studied. Ulysses transpositions occur only in the strain where antisense piRNAs homologous to this TE are virtually absent and the ping-pong amplification loop apparently does not take place. On the other hand small RNAs homologous to Penelope found in the other strain, belong predominantly to the siRNA category (21nt), and consist of sense and antisense species observed in approximately equal proportion. The number of Penelope copies in the latter strain has significantly increased during the last decades, probably because Penelope-derived siRNAs are not maternally inherited, while the low level of Penelope-piRNAs, which are faithfully transmitted from mother to the embryo, is not sufficient to silence this element completely. Therefore, we speculate that intrastrain transposition of the three retroelements studied is controlled predominantly at the post-transcriptional level.
To Be Mobile or Not: The Variety of Reverse Transcriptases and Their Recruitment by Host Genomes
Biochemistry (Moscow), 2023
Reverse transcriptases (RT), or RNA-dependent DNA polymerases, are unorthodox enzymes that originally added a new angle to the conventional view of the unidirectional f low of genetic information in the cell from DNA to RNA to protein. First discovered in vertebrate retroviruses, RTs were since rediscovered in most eukaryotes, bacteria, and archaea, spanning essentially all domains of life. For retroviruses, RTs provide the ability to copy the RNA genome into DNA for subsequent incorporation into the host genome, which is essential for their replication and survival. In cellular organisms, most RT sequences originate from retrotransposons, the type of self-replicating genetic elements that rely on reverse transcription to copy and paste their sequences into new genomic locations. Some retroelements, however, can undergo domestication, eventually becoming a valuable addition to the overall repertoire of cellular enzymes. They can be beneficial yet accessory, like the diversity-generating elements, or even essential, like the telomerase reverse transcriptases. Nowadays, ever-increasing numbers of domesticated RT-carrying genetic elements are being discovered. It may be argued that domesticated RTs and reverse transcription in general is more widespread in cellular organisms than previously thought, and that many important cellular functions, such as chromosome end maintenance, may evolve from an originally selfish process of converting RNA into DNA.
Cell, 1982
We have identified a lethal mutation in the D. melanogaster RNA polymerase II locus, RP/lc4, caused by insertion of a transposable element associated with the phenomenon of hybrid dysgenesis (P element). Using previously cloned P element sequences as a hybridization probe we have isolated a hybrid lambda phage clone carrying a 10 kb genomic DNA fragment containing a 1.3 kb P element insert and flanking sequences from the Rpl/ locus. The non-P sequences in this clone (XDmRpll-1) hybridize to polytene chromosome band region lOC, the cytogenetic location of Rpllc4, and revertants which lose the lethal RNA polymerase II mutation also lose P element sequences from the locus. We have generated several additional P element insertions into the locus and shown that they can occur at two or more different sites. These experiments illustrate that mutagenesis by P element insertion and use of cloned P DNA to retrieve the DNA sequences into which insertion has occurred may be a general method for cloning genetically defined loci in Drosophila.
A reverse transcriptase ribozyme
A highly evolved RNA polymerase ribozyme was found to also be capable of functioning as a reverse transcriptase, an activity that has never been demonstrated before for RNA. This activity is thought to have been crucial for the transition from RNA to DNA genomes during the early history of life on Earth, when it similarly could have arisen as a secondary function of an RNA-dependent RNA polymerase. The reverse transcriptase ribozyme can incorporate all four dNTPs and can generate products containing up to 32 deoxynucleotides. It is likely that this activity could be improved through evolution, ultimately enabling the synthesis of complete DNA genomes. DNA is much more stable compared to RNA and thus provides a larger and more secure repository for genetic information.
Nucleic Acids Research, 1988
Used at a physiological concentration, the steroid hormone 20-hydroxyecdysone (20-OHE) induces, in Kc cultured Drosophila melanogaster cells, important and specific changes. Modifications occur at morphological and enzymatical levels. Variations in specific protein synthesis are observed. At the molecular level, 20-OHE particularly induces a decrease in expression of the mobile dispersed genetic element 412. This repeated element which belongs to the "copia-like" family is more widely represented in Kc cells (80 fold) compared to fly cells (25 fold). 412 transcripts are heterogeneous in size, essentially polyadenylated and restricted to the nucleus. A minimal concentration of 10-8 M and a time treatment of 16 hours are necessary to obtain a strong decrease in 412 expression. The decrease is at least an effect on these sequences at the transcriptional level. Structural similarities between the 412 element and the proviral forms of vertebrate retroviruses are strenghtened by the characterization of extrachromosomal circular DNA forms revealed by the 412 probe. Quantifying experiments have shown that the steady state level of such forms is not affected by the steroid treatment.