Functional analysis of point mutations in the AAUAAA motif of the SV40 late polyadenylation signal.

We have constructed 14 independent point mutations in the conserved AAUAAA element of the SV40 late polyadenylation signal in order to study the recognition and function of alternative polyadenylation signals. A variant RNA containing an AUUAAA was polyadenylated at 20% the level of wild-type substrate RNA, while all other derivatives tested were not functional in vitro. The AUUAAA variant RNA formed specific complexes in native polyacrylamide gels and crosslinked to the AAUAAA-specific 64kd polypeptide, but at a lower efficiency than wild-type substrate RNA.