THE YEAST SME1 GENE ENCODES THE HOMOLOG OF THE HUMAN-E CORE PROTEIN

Removal of introns from pre-messenger RNA (pre-mRNA) requires small nu clear RNAs (snRNAs) packaged into stable small ribonucleoprotein parti cles (snRNP). These snRNPs contain specific and common proteins also c alled Sm proteins. Correct assembly of the snRNAs with the common prot eins is an essential step for the biogenesis of snRNP particles. We ha ve identified a new Saccharomyces serevisiae gene, SME1 whose product shows 45% identity with the E core protein of human snRNP. The Sme1p c ontains 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 U 1, U2, U4 and U5 snRNA stability. We show also that the human E core p rotein complements a yeast SME1 disruption demonstrating the functiona l equivalence of Sme1p and the human E core protein.