This entry represents Sm-like protein Lsm4. It could be found in the nuclear Lsm2-8 complex or in the cytoplasmic Lsm1-7 complex. The Lsm2-8 complex associates with multiple snRNP complexes containing the U6 snRNA (U4/U6 snRNP, U4/U6.U5 snRNP, and free U6 snRNP). It binds and stabilizes the 3'-terminal poly(U) tract of U6 snRNA and facilitates the assembly of U4-U6 di-snRNP and U4-U6-U5 tri-snRNP [, , ]. The Lsm1-7 complex associates with deadenylated mRNA and promotes decapping in the 5'-3' mRNA decay pathway [, ]. The Sm and the Lsm proteins, characterised by the Sm-domain, have RNA-related functions. The Sm heptamer ring associates with four (U1, U2, U4, U5) snRNPs, while Lsm2-8 heptamer associates with the U6 snRNP. Another Lsm heptameric complex, Lsm1-7, which differs from Lsm2-8 by one Lsm protein, functions in mRNA decapping, a crucial step in the mRNA degradation pathway [].
This entry represents a group of LSM domain containing proteins functioning in RNA processing, including U6 snRNA-associated Sm-like protein LSm4 and small nuclear ribonucleoproteins Sm D1 and D3.LSm4 is a component of LSm protein complexes, which are involved in RNA processing and may function in a chaperone-like manner. It binds specifically to the 3'-terminal U-tract of U6 snRNA [, ]. SmD1 is involved in pre-mRNA splicing. It binds snRNA U1, U2, U4 andU5, which contain a highly conserved structural motif called the Sm binding site. It also binds telomerase RNA and is required for its accumulation [, ].SmD3 is a core protein of small nuclear ribonucleoprotein (snRNP) essential for splicing of primary transcripts []. It appears to function in the U7 snRNP complex that is involved in histone 3'-end processing. It binds to the downstream cleavage product (DCP) of histone pre-mRNA in a U7 snRNP dependent manner [].
