STRUCTURAL FEATURES OF U6 SNRNA AND DYNAMIC INTERACTIONS WITH OTHER SPLICEOSOMAL COMPONENTS LEADING TO PRE-MESSENGER-RNA SPLICING

In the spliceosome, the pre-mRNA, U2 and U6 snRNAs fold into a catalyt ic structure exhibiting striking similarities with domain V and VI of group II introns. Building of this tripartite structure implies that a n evolutionary conserved base pairing between U4 and U6 snRNAs should be disrupted to allow potentially U6 catalytic residue to interact wit h U2 snRNAs and the pre-mRNA. The steps leading to U4/U6 disruption ha ve been recently discovered and have been shown to involve a modificat ion of the 3' end of U6 snRNA and the hnRNP C protein.