Reverse transcriptase-related proteins in telomeres and in certain chromosomal loci of Rhynchosciara (Diptera: Sciaridae)

Gorab, Eduardo

doi:10.1007/s00412-003-0229-5

Cited by 24 publications

(33 citation statements)

References 36 publications

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“…In these organisms that lack telomerase, the involvement of an enzyme with reverse transcriptase activity in the telomere maintenance and its nucleolar localization has been suggested as an essential element for maintaining the integrity of chromosome ends (Díez et al 2006). The same protein was located on polytene chromosomes of salivary glands in nontelocentric regions in Rhynchosciara americana (Gorab 2003).…”

Section: Electronic Supplementary Materialsmentioning

confidence: 97%

Molecular characterization of a retrotransposon in the Rhynchosciara americana genome and its association with telomere

et al. 2008

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Non-LTR retrotransposons, also known as long interspersed nuclear elements (LINEs), are transposable elements that encode a reverse transcriptase and insert into genomic locations via RNA intermediates. The sequence analysis of a cDNA library constructed from mRNA of the salivary glands of R. americana showed the presence of putative class I elements. The cDNA clone with homology to a reverse transcriptase was the starting point for the present study. Genomic phage was isolated and sequenced and the molecular structure of the element was characterized as being a non-LTR retrotransposable element. Southern blot analysis indicated that this transposable element is represented by repeat sequences in the genome of R. americana. Chromosome tips were consistently positive when this element was used as probe in in-situ hybridization. Real-time RT-PCR showed that this retrotransposon is transcribed at different periods of larval development. Most interesting, the silencing of this retrotransposon in R. americana by RNA interference resulted in reduced transcript levels and in accelerated larval development.

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Section: Electronic Supplementary Materialsmentioning

confidence: 97%

Molecular characterization of a retrotransposon in the Rhynchosciara americana genome and its association with telomere

et al. 2008

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“…These may function as retrotransposition intermediates involved in RT activity. Interestingly, RT has also been found in diVerent species of sciarids (Diptera), in which it appears to be strongly associated with the telomeres (Gorab 2003). In this hypothesis, RT activity would be an essential element for maintaining telomere integrity, despite the diversity of telomeric sequences found in these insects.…”

Section: Introductionmentioning

confidence: 93%

Nucleolar localization of a reverse transcriptase related to telomere maintenance in Chironomus (Diptera)

Díez

Vilariño

Medina

et al. 2006

Histochem Cell Biol

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A growing number of cellular processes originally thought not to involve the nucleolus now seem to be associated with this organelle. In recent years, a variety of RNAs and proteins with no apparent function in ribosome genesis have been discovered in this nuclear compartment. This paper reports the presence in the nucleolus of a reverse transcriptase (RT) previously found to be associated with telomeres in Chironomus. Immunofluorescence detection using a specific antibody against conserved domains shared by RTs showed a distinct pattern of staining in the giant nucleoli of polytenized cells. This nucleolar localization was confirmed in a number of larval tissues and embryonic cells of Chironomus thummi and C. pallidivitatus; its distribution showed a definite necklace pattern that did not completely colocalize with fibrillarin or nucleolin and appeared to be different to that of typical nucleolar components. There is evidence that both telomerase RT and RNA template subunits are present in the nucleoli of mammalian and yeast cells. However, chironomids do not have typical telomeres or telomerase. As in other Diptera, telomeres lack the short, simple repeats maintained by telomerase and instead have more complex sequences in the range of hundreds of nucleotides. It has been suggested that the RT associated with these telomeres might be involved in their maintenance, perhaps involving a mechanism similar to that of telomerase retrotranscription and retrotransposition in Drosophila. The present results indicate that the putative Chironomus telomere elongation machinery and telomerase share a nucleolar localization. This reinforces the idea that nucleoli are functionally linked to telomere maintenance irrespective of the differences in their molecular organization and therefore in the strategy adopted for their elongation.

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“…The complex repetitive sequences found in Chironomus telomeres must be functionally homologous to the other types of telomeric DNA and, most probably, are involved in the telomere-maintenance mechanism of these organisms. The localization of reverse transcriptase in Chironomid telomeres (López et al 1999, Gorab 2003, Díez et al 2006 suggests that retrotranscription processes could also be involved in the maintenance mechanism of these atypical telomeres. In addition, Ku and HSP90 proteins, related to telomerase telomeres, were also found associated with Chironomus telomeres (Gorab et al 1996, Morcillo et al 1993.…”

Section: Introductionmentioning

confidence: 97%

Transcription and activation under environmental stress of the complex telomeric repeats of Chironomus thummi

2008

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In contrast to their traditional role, telomeres seem to behave as transcriptionally active regions. RNAs complementary to the short DNA repeats characteristic of telomerase-maintained telomeres have recently been identified in various mammalian cell lines, representing a new and unexpected element in telomere architecture. Here, we report the existence of transcripts complementary to telomeric sequences characteristic of Chironomus thummi telomeres. As in other Diptera, the non-canonical telomeres of chironomids lack the simple telomerase repeats and have instead more complex repetitive sequences. Northern blots of total RNA hybridized with telomere probes and RT-PCR with telomere-specific tailed primers confirm the existence of small non-coding RNAs of around 200 bp, the size of the DNA repeated telomeric unit. Telomere transcripts are heterogeneous in length, and they appear as a ladder pattern that probably corresponds to multimers of the repeat. Moreover, telomeres are activated under conditions of environmental stress, such as heat shock, appearing highly decondensed and densely labelled with acetylated H4 histone, as well as with RNA polymerase II antibodies, both marks of transcriptional activity. Changes in the expression levels of telomeric RNA were detected after heat shock. These findings provide evidence that transcriptional activity of the repetitive telomere sequences is an evolutionarily conserved feature, not limited to telomerase telomeres. The functional significance of this non-coding RNA as a new additional element in the context of telomere biology remains to be explained.

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Reverse transcriptase-related proteins in telomeres and in certain chromosomal loci of Rhynchosciara (Diptera: Sciaridae)

Cited by 24 publications

References 36 publications

Molecular characterization of a retrotransposon in the Rhynchosciara americana genome and its association with telomere

Molecular characterization of a retrotransposon in the Rhynchosciara americana genome and its association with telomere

Nucleolar localization of a reverse transcriptase related to telomere maintenance in Chironomus (Diptera)

Transcription and activation under environmental stress of the complex telomeric repeats of Chironomus thummi

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