InterPro domain: IPR022023

This domain is about 90 amino acids in length and is found at the N terminus of U1 small nuclear ribonucleoprotein 70kDa (U1-70K), which is part of the U1 snRNP (snRNP) complex. U1 snRNP recognises the 5' splice site within precursor messenger RNAs and initiate the assembly of the spliceosome for intron excision.

The N-terminal region of U1-70K extends over a distance of 180 A from its RNA binding domain, wraps around the core domain of U1 snRNP consisting of the seven Sm proteins and finally contacts U1-C, which is crucial for 5'-splice-site recognition [ 1 ].

1. Crystal structure of human spliceosomal U1 snRNP at 5.5 A resolution. Nature 458, 475-80