InterPro domain: IPR027078

Small nuclear ribonucleoprotein E (SME1) is involved in pre-mRNA splicing. It is required for pre-mRNA splicing, cap modification and for the stability of snRNA U1, U2, U4 and U5 [ 1 , 2 ].

The eukaryotic Sm proteins (B/B', D1, D2, D3, E, F and G) assemble into a hetero-heptameric ring around the Sm site of the 2,2,7-trimethyl guanosine (m3G) capped U1, U2, U4 and U5 snRNAs (Sm snRNAs) forming the core of the snRNP particle. The snRNP particle, in turn, assembles with other components onto the pre-mRNA to form the spliceosome which is responsible for the excision of introns and the ligation of exons [ 3 , 4 ]. Members of this family share a highly conserved Sm fold containing an N-terminal helix followed by a strongly bent five-stranded antiparallel beta-sheet [ 5 ]. Sm subunit E binds subunits F and G to form a trimer which then assembles onto snRNA along with the D1/D2 and D3/B heterodimers forming a seven-membered ring structure [ 5 ].

1. The yeast SME1 gene encodes the homologue of the human E core protein. Gene 176, 111-7
2. Lsm proteins and RNA processing. Biochem. Soc. Trans. 33, 433-8
3. The Sm domain is an ancient RNA-binding motif with oligo(U) specificity. Proc. Natl. Acad. Sci. U.S.A. 98, 3685-9
4. Sm protein-Sm site RNA interactions within the inner ring of the spliceosomal snRNP core structure. EMBO J. 20, 187-96