Homologous recombination during meiosis is essential to ensure proper chromosome segregation. Improper chromosome segregation can lead to meiotic aneuploidy, which is the leading cause of congenital birth defects, mental retardation, and spontaneous pregnancy loss in humans. Errors in the positioning and frequency of recombination are features of all meiotic aneuploidies studied. Meiotic homologous recombination is induced by double-stranded DNA (dsDNA) breaks and is clustered preferentially at recombination hotspots, such as the ade6-M26 hotspot in the fission yeast Schizosaccharomyces pombe.
Evidence that transcription helps activate the ade6-M26 hotspot includes the binding of Atf1, an ATF/CREB transcription factor, to a CRE-like DNA site, M26, that is required for hotspot activity. The ade6 promoter is also essential for hotspot activity. Interestingly, these hotspot-activating factors also trigger the formation of a short, hotspot-specific RNA. In this dissertation, it is reported that no single discrete site in the promoter is required for hotspot activity or hotspot RNA production, as evidenced by a functional dissection of the ade6 promoter region. Hotspot RNA is induced in meiosis and under stress conditions in an Atf1-dependent manner. Furthermore, hotspot RNA is processed post-transcriptionally in a pathway that is distinct from both nonsense-mediated decay and RNA interference. These results provide evidence of a previously unknown mechanism of post-transcriptional gene regulation by ATF/CREB proteins. M26 DNA sites moved along the ade6 open reading frame that have hotspot activity also produce short RNA transcripts whose 5' ends map near the M26 sites as do dsDNA breaks. These data suggest that hotspot RNA may help direct the positioning of recombination-initiating dsDNA breaks.
Neither artificially shortened ade6-M26 RNA nor hotspot RNA is sufficient for hotspot activity. However, loss of processed hotspot RNA results in a 50% reduction in hotspot activity. These results indicate that hotspot RNA is required for full hotspot activity at ade6-M26 , although it is not essential for all hotspot activity. This dissertation work shows that a specific processed RNA molecule is required for the full activity of a meiotic recombination hotspot, increasing the number of processes known to be mediated, at least in part, by RNA or RNA metabolism.
|Advisor:||Wahls, Wayne P.|
|School:||University of Arkansas for Medical Sciences|
|School Location:||United States -- Arkansas|
|Source:||DAI-B 70/04, Dissertation Abstracts International|
|Subjects:||Molecular biology, Genetics|
|Keywords:||Hotspot, Meiosis, RNA, Recombination, Yeast|
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