This entry represents Sm-like protein Lsm7. 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 is part of 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 [].
Small nuclear ribonucleoproteins (snRNPs) are components of major and minor spliceosomes that play an important role in the splicing of cellular pre-mRNAs. snRNPs contain a common core, composed of seven Sm proteins bound to snRNA. Five small snRNPs (U1, U2, U4 and U5) share the Sm heptamer ring composed of SmB/B', SmD1/2/3, SmE, SmF, and SmG (also known as snRNP-G), while U6 snRNP has aheptamer ring consist of seven Sm-like (Lsm) proteins: Lsm2, Lsm3, Lsm4, Lsm5, Lsm6, Lsm7 and Lsm8 []. This entry includes the snRNP heptamer ring components SmF (small nuclear ribonucleoprotein F), Lsm6 and LSM36B from Arabidopsis[].
