Could Poly(A) Align the Splicing Sites of Messenger RNA Precursors?

In general, poly(A)-mRNA appears to be derived from larger nuclear RNA precursors. The maturation of these precursors involves excision of sequences of variable length from within the molecule and splicing of the remaining structural and coding sequences. The mechanism by which this process occurs is not known. It does not appear to operate solely through the recognition of a defined primary sequence or through the formation of a consistent secondary structure. We propose an alternative model in which poly(A) facilitates the splicing event by promoting the formation of triple-stranded structures within the mRNA precursor.