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Identifier 000412900
Title Λειτουργική ανάλυση του γονιδίου Snipper στη Drosophila melanogaster
Alternative Title Functional analysis of Snipper gene in Drosophila melanogaster
Author Αλεξιάδης, Αναστάσιος
Thesis advisor Καλαντίδης, Κρίτων
Reviewer Αλεξανδράκη, Δέσποινα
Βόντας, Ιωάννης
Δελιδάκης, Χρήστος
Καμπράνης, Σωτήριος
Τσαγρή, Ευθυμία
Χαλεπάκης, Γεώργιος
Abstract ERI-1 (Enhanced RNAi) is an RNA exonuclease that was identified in a genetic screen in Ceanorabditis elegans as a negative regulator of RNA interference (RNAi). It has been proposed that ERI-1 exerts its action through the excision of the two protruding 3’ nucleotides that are present in siRNAs. This excision renders the siRNAs unfunctional. ERI-1 homologues in Homo sapiens and Mus musculus are interacting with 3’ end of histone mRNAs, participating in their maturation through the removal of two terminal nucleotides and their turnover at the end of S phase. Additionally ERI-1 in Schizosaccharomyces pombe, Ceanorabditis elegans and Mus musculus is involved in 5.8S rRNA maturation snipping 2 nucleotides from its 3’ end. It is apparent that ERI-1 is an important exonuclease implicated in basic RNA mediated cellular mechanisms. For this reason we chose to investigate its function in Drosophila melanogaster where our knowledge has been limited to the biochemical characterization of the ERI-1 homologue Snipper (Snp) as an exonuclease. We used transposable element insertion lines in Snp, suppression of its expression through RNAi and overexpressing transgenic lines in order to assess its involvement in known pathways. Our results establish Snp as an important gene for normal Drosophila melanogaster development since it is a maternally provided transcript and reduction of its levels leads to developmental arrest in specific stages. Additionally, compromising Snp expression in various tissues causes abnormal phenotypes. In accordance to the atypical biogenesis of 5.8S rRNA in Drosophila melanogaster, it does not appear to be affected by the lack of Snp. On the contrary, in the case of the histonic transcripts we detected a significant reduction of their abundance upon Snp depletion. This reduction is most likely a direct effect, since Snp protein and histone mRNA physically interact as it was manifested by immunoprecipitation experiments. Additionally sequencing of histone 3 mRNA 3’ ends revealed that its processing is altered in the absence of Snp. Our hypothesis is that Snp participates in the maturation and protection of 3’ end of histonic mRNAs and its absence leads to reduced histone mRNA levels possibly through increased degradation. This in turn may lead to cell cycle delay or arrest causing the observed phenotypes.
Language Greek
Issue date 2017-12-14
Collection   Faculty/Department--Faculty of Sciences and Engineering--Department of Biology--Doctoral theses
  Type of Work--Doctoral theses
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