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Role of Nab2 in RNA metabolism in Saccharomyces cerevisiae

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandlingForskning

  • Pawel Olszewski, Danmark
Proper assembly of export-competent mRNP is a key step in gene expression. It requires the concerted action of multiple protein factors. In addition, different steps of mRNP biogenesis are mutually related and tight coordination between processing events is required. Yet, the high complexity of mRNP assembly generates errors, which are tracked down by nuclear surveillance mechanisms. Thus, not surprisingly, protein components of mRNPs have multiple functions in the biogenesis of the particle but also interact with the surveillance machinery. An example of such a multifunctional factor is the S. cerevisiae Nab2 protein. It has been associated with poly(A) tail synthesis and mRNA export. However, recently it was proposed to also interact with the nuclear exoribonuclease Rrp6 and mediate the degradation of pre-mRNAs. This unexpected finding prompted me to investigate its role in more detail. Here, I present further evidence for an essential role of Nab2 in general mRNP biogenesis and a novel function in the biogenesis of small nucleolar RNAs (snoRNAs). Utilization of a rapid protein depletion system revealed a robust mRNA destabilization in the absence of Nab2, which was additionally confirmed by metabolic labeling experiments. Interestingly, experiments in NAB2 mutants showed opposite effects between protein N- and C-terminal truncations on both mRNA and pre-mRNA stability. This suggests that Nab2 can both protect from, and promote, transcript degradation. Consistently, proteomic analysis of mRNP components showed changes in the Nab2 interactome in the absence of Rrp6, and also suggested that Nab2 binds to multiple sites on the mRNA. Wide-range proteomic analysis of Nab2 immunoprecipitates revealed association with C/D box snoRNP components. These novel interactions were supported by the presence of snoRNAs in Nab2-bound RNA fractions. Moreover, obtained data indicate that Nab2 may be required for the processing of snoRNAs that have their precursors generated through the CFI-CPF termination pathway. Altogether, my results place Nab2 among the essential factors required for mRNP stability, hereby contributing to the overall complexity of RNP dynamics.
OriginalsprogEngelsk
ForlagUniversity of Aarhus, Faculty of Science
Antal sider112
Rekvirerende organGraduate School of Science and Technology
StatusUdgivet - 14 aug. 2013

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