The yeast SME1 gene encodes the homologue of the human E core protein

Removal of introns from pre-messenger RNA (pre-mRNA) requires small nuclear RNAs (snRNAs) packaged into stable small ribonucleoprotein particles (snRNP). These snRNPs contain specific and common proteins also called Sm proteins. Correct assembly of the snRNAs with the common proteins is an essential step for the biogenesis of snRNP particles. We have identified a new Saccharomyces serevisiae gene, SME1 whose product shows 45% identity with the E core protein of human snRNP. The Sme1p contains the evolutionary conserved residues found in all Sm proteins. Combining genetic and biochemical experiments, we show that SME1 is an essential gene required for pre-mRNA splicing, cap modification and U1, U2, U4 and U5 snRNA stability. We show also that the human E core protein complements a yeast SME1 disruption demonstrating the functional equivalence of Sme1p and the human E core protein.