With the exception of histone transcripts, all eukaryotic mRNAs undergo a process of 3’ end maturation. mRNA 3’ processing involves a large multi-protein complex, called the cleavage and polyadenylation specificity factor (CPSF), which recognizes the AAUAAA site as a polyadenylation signal. Two independent papers in the upcoming issue of G&D lend new insight into the recognition of the poly(A) site by CPSF, and overturn a long-held belief about this process. Schönemann and colleagues characterized CPSF subunits, finding that only 4 are needed for CPSF function in polyadenylation and, furthermore, that the WDR33 subunit – not CPSF160, as was previously thought –is responsible for recognition of the poly(A) signal. Using an entirely different experimental system, Chan and colleagues reached the same conclusion and documented a crucial role for a second CPSF subunit, CPSF30, in binding CPSF to the AAUAAAA site. Interestingly, this study also provided evidence that the influenza virus has evolved to precisely target the CPSF30-AAUAAA interaction in order to suppress host gene expression. Given the current interest in alternative 3’ end processing as a means to alter 3’ UTR length and thus interactions between the transcript and miRNAs and/or RNA-binding proteins, these findings are expected to be of interest to a broad audience.
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