Downstream sequence elements with different affinities for the hnRNP H/H′ protein influence the processing efficiency of mammalian polyadenylation signals

TL;DR: Using in vitro reconstitution assays, it is demonstrated that hnRNP H/H' can stimulate processing of two additional model polyadenylation signals by binding at similar relative downstream locations but with significantly different affinities.

Abstract: Auxiliary factors likely play an important role in determining the polyadenylation efficiency of mammalian pre-mRNAs We previously identified an auxiliary factor, hnRNP H/H', which stimulates 3'-end processing through an interaction with sequences downstream of the core elements of the SV40 late polyadenylation signal Using in vitro reconstitution assays we have demonstrated that hnRNP H/H' can stimulate processing of two additional model polyadenylation signals by binding at similar relative downstream locations but with significantly different affinities A short tract of G residues was determined to be a common property of all three hnRNP H/H' binding sites A survey of mammalian polyadenylation signals identified potential G-rich hnRNP H/H' binding sites at similar downstream locations in approximately 34% of these signals All of the novel G-rich elements tested were found to bind hnRNP H/H' protein and the processing of selected signals identified in the survey was stimulated by the protein both in vivo and in vitro Downstream G-rich tracts, therefore, are a common auxiliary element in mammalian polyadenylation signals Sequences capable of binding hnRNP H protein with varying affinities may play a role in determining the processing efficiency of a significant number of mammalian polyadenylation signals