The U1 snRNP binds to the 5-prime splice site of precursor mRNAs, and is composed of the U1 snRNA ; 3 specific proteins, called 70K (SNRP70), A (SNRPA), and C (SNRPC); and several common proteins also found in other snRNPs. The predicted 297-amino acid protein contains a hydrophilic region, an internal sequence duplication, and an RNP consensus domain common to RNA-binding proteins. By SDS-PAGE, SNRPA has a molecular mass of 32 kD. SNRPA shares 2 regions of homology with SNRPB2, a component of the U2 snRNP particle, and the proteins are structurally related. The authors suggested that although SNRPA and SNRPB2 are located in different snRNP particles, they may have identical functions. Northern blot analysis indicated that the SNRPA gene is expressed as a 1.4-kb mRNA.