RNA-binding protein that specifically binds distinct small nuclear RNA (snRNAs) and regulates their processing and function. Specifically binds the 7SK snRNA (7SK RNA) and acts as a core component of the 7SK ribonucleoprotein (RNP) complex, thereby acting as a negative regulator of transcription elongation by RNA polymerase II. The 7SK RNP complex sequesters the positive transcription elongation factor b (P-TEFb) in a large inactive 7SK RNP complex preventing RNA polymerase II phosphorylation and subsequent transcriptional elongation. The 7SK RNP complex also promotes snRNA gene transcription by RNA polymerase II via interaction with the little elongation complex (LEC). LARP7 specifically binds to the highly conserved 3'-terminal U-rich stretch of 7SK RNA; on stimulation, remains associated with 7SK RNA, whereas P-TEFb is released from the complex. LARP7 also acts as a regulator of mRNA splicing fidelity by promoting U6 snRNA processing. Specifically binds U6 snRNAs and associates with a subset of box C/D RNP complexes: promotes U6 snRNA 2'-O-methylation by facilitating U6 snRNA loading into box C/D RNP complexes. U6 snRNA 2'-O-methylation is required for mRNA splicing fidelity. Binds U6 snRNAs with a 5'-CAGGG-3' sequence motif (By similarity). U6 snRNA processing is required for spermatogenesis (By similarity).
Subcellular locations: Nucleus, Nucleoplasm