U1 small nuclear ribonucleoprotein (U1 snRNP)

U1 small nuclear ribonucleoprotein (U1 snRNP) is a multi-subunit ribonucleoprotein complex involved in the recognition of the 5’ splice site at the exon-intron junction of precursor mRNA (pre-mRNA). It consists of U1 small nuclear RNA (164 bases), seven common Sm proteins (SmB/B', SmD1, SmD2, SmD3, SmE, SmF, SmG), and three U1-specific proteins (U1-70K, U1-A, U1-C). U1 snRNP binds to the 5’ splice site through base pairing between U1 snRNA and the pre-mRNA, thereby initiating spliceosome assembly. Its structure features a Sm protein ring core, with RNA stem-loops interacting with specific proteins. U1 snRNP is critical not only for canonical splicing but also plays roles in alternative polyadenylation regulation. Beyond its molecular functions, U1 snRNP has clinical relevance as an autoantigen in certain systemic autoimmune diseases, detected by specific autoantibodies[1][2][3][4][5][6][7][8].

Other names

U1 snRNPU1 spliceosomal RNPU1 particleU1 small nuclear RNP

When targeted experimentally, actions include blocking U1 snRNA—leading to inhibition of spliceosome assembly or altered splicing site usage (e.g., antisense oligonucleotides cause alternative polyadenylation and shorter transcripts)