Small nuclear ribonucleoprotein D3 polypeptide (SNRPD3) (Sm-D3)

Small nuclear ribonucleoprotein D3 polypeptide (Sm-D3) is a core component of the spliceosome, specifically part of the U1, U2, U4, and U5 small nuclear ribonucleoprotein (snRNP) complexes. It plays a fundamental role in pre-mRNA splicing by forming a heptameric ring with other Sm proteins around snRNA. Beyond its role in RNA processing, Sm-D3 has been implicated in DNA double-strand break repair through the stabilization of RAD51 and CHK1 at damage sites. In the context of disease, Sm-D3 is a major autoantigen in systemic lupus erythematosus (SLE), where autoantibodies specifically target its carboxyl-terminal glycine-arginine rich domain, particularly when modified by symmetrical dimethylation. In oncology, Sm-D3 is a downstream effector of PRMT5, and its aberrant methylation supports the survival of cancer cells by facilitating the splicing of oncogenic transcripts and promoting DNA repair. Consequently, Sm-D3 and its post-translational modifications are explored as both diagnostic biomarkers and therapeutic vulnerabilities in autoimmune and malignant conditions.

Other names

SmD3SMD3snRNP core protein D3Small nuclear ribonucleoprotein Sm D3Smith antigen D3 subunit

Inhibition of PRMT5 prevents the symmetrical dimethylation of Sm-D3, which is required for its assembly into snRNPs and its role in oncogenic splicing and DNA repair.