SNRPA associates with stem loop II of the U1 small nuclear ribonucleoprotein, which binds the 5’ splice site of precursor mRNAs and is essential for splicing. The SNRPA protein autoregulates itself by polyadenylation inhibition of its own pre-mRNA via dimerization and is involved in the coupling of splicing and polyadenylation. SNRPA binds stem loop II of U1 snRNA. SNRPA is the first snRNP to interact with pre-mRNA. This interaction is vital for the subsequent binding of U2 snRNP and the U4/U6/U5 tri-snRNP.