A large inverted repeat sequence overlaps two acceptor splice sites in adenovirus.

The distribution of nucleotide sequences resembling functional sites for mRNA splicing was examined by computer-directed searches in order to determine what factors may influence splice site selection in nuclear precursors. In particular, the distribution of large potentially stable hairpin structures or regions of extensive dyad symmetry was studied in adenovirus sequences. One region, spanning 106 nucleotides, was found at 66.4 map units, overlapping back-to-back acceptor sites for two mRNA molecules, those coding for the 100K protein and the 72K DNA binding protein, which are transcribed from opposite strands. This region displays exceptional dyad symmetry and is potentially capable of forming a single, highly stable hairpin when transcribed. It seems likely that the secondary structure as well as the primary structure of RNA plays a role in determining the correct splicing of these mRNA molecules.