RRM
2011 Rustbelt RNA Meeting
RRM
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Poster abstracts
Abstract:
Messenger RNA Polyadenylation [Poly(A)] plays crucial molecular functions including preventing mature mRNA from degradation and recognition by the transport apparatus for cytoplasmic exportation and by the translational initiation complex for translation. In this study, we analyzed the genomes of eleven eukaryotic species (two diatoms, two green algae, red alga, ciliate, moss, spikemoss, Arabidopsis, yeast and human) for cis-elements around poly(A) sites, particularly in the Near Upstream Element (NUE) region located right before the poly(A) sites. For all species analyzed, there is a complex transition of nucleotide composition around the poly(A) sites and within the NUE region. Considering both the frequency and significance of poly(A) signals in the NUE region, while yeast and ciliate do not have much conserved signals, a triplet (UAA) and two tetramers (UAAA and GUAA) were found dominant in diatoms and red alga respectively. The green algae and humans possess high frequency and extremely conserved UGUAA and AAUAAA signals respectively. The remaining embryophytes, including moss, spikemoss and Arabidopsis, use the conserved AAUAAA signal but in low frequency (~8%), which implied that somewhat different mechanisms is used in polyadenylation process in embryophytes. The single nucleotide variants from AAUAAA suggested that the first two bases (i.e., NNUAAA) are degenerated and hence highly flexible whereas UAAA are the core part of the motif, which is consistent with wet-lab study results of polyadenylation signal efficiency. Comparing the poly(A) signals in the examined eleven species, our results suggest that AAUAAA and its variants are derived from UAA with an intermediate status of UAAA. However, the UGUAA signal might follow an independent evolutionary path.
Keywords: polyadenylation, evolution, poly(A) signal
