Capped mRNA degradation intermediates accumulate in the yeast spb8-2 mutant

mRNA in the yeast Saccharomyces cerevisiae is primarily degraded through a pathway that is stimulated by removal of the mRNA cap structure. Here we report that a mutation in the SPB8 (YJL124c) gene, initially identified as a suppressor mutation of a poly(A)-binding protein (PAB1) gene deletion, stabilizes the mRNA cap structure. Specifically, we find that the spb8-2 mutation results in the accumulation of capped, poly(A) deficient mRNAs. The presence of this mutation also allows for the detection of mRNA species trimmed from the 3' end. These data show that this Sm-like protein family member is involved in the process of mRNA decapping, and they provide an example of 3'-5' mRNA degradation intermediates in yeast.