THE SPLICING FACTOR BBP INTERACTS SPECIFICALLY WITH THE PRE-MESSENGER-RNA BRANCHPOINT SEQUENCE UACUAAC

The yeast splicing factor BBP (branchpoint bridging protein) interacts directly with pre-mRNA at or very near the highly conserved branchpoi nt sequence UACUAAC within the commitment complex. We also show that t he recombinant protein recognizes the UACUAAC sequence. Therefore, BBP is also an acronym for branchpoint binding protein. The mammalian spl icing factor SF1 is a BBP ortholog (mBBP) and an E complex component, and also has branchpoint sequence specificity. The relative conservati on of this region in yeast and mammals correlates well with the RNA-bi nding differences between BBP and mBBP, suggesting that BBP contribute s to branchpoint sequence definition in both systems.