THE SCHIZOSACCHAROMYCES-POMBE PLA1 GENE ENCODES A POLY(A) POLYMERASE AND CAN FUNCTIONALLY REPLACE ITS SACCHAROMYCES-CEREVISIAE HOMOLOG

We have isolated the poly(A) polymerase (PAP) encoding gene pla1 [for poly(A) polymerase] from the fission yeast Schizosaccharomyces pombe. Protein sequence alignments with other poly(A) polymerases reveal that pla1 is more closely related to Saccharomyces cerevisiae PAP than to bovine PAP The two yeast poly(A) polymerases share significant sequenc e homology not only in the generally conserved N-terminal part but als o in the C-terminus. Furthermore, pla1 rescues a S.cerevisiae PAP1 dis ruption mutant, An extract from the complemented strain is active in t he specific in vitro polyadenylation assay. In contrast, recombinant P LA1 protein can not replace bovine PAP in the mammalian in vitro polya denylation assay. These results indicate a high degree of conservation of the polyadenylation machinery among the evolutionary diverged budd ing and fission yeasts.