FUNCTIONAL-ANALYSIS OF THE FISSION YEAST PRP4 PROTEIN-KINASE INVOLVEDIN PRE-MESSENGER-RNA SPLICING AND ISOLATION OF A PUTATIVE MAMMALIAN HOMOLOG

The prp4 gene of Schizosaccharomyces pombe encodes a protein kinase, A physiological substrate is not yet known, A mutational analysis of pr p4 revealed that the protein consists of a short N-terminal domain, co ntaining several essential motifs, which is followed by the kinase cat alytic domain comprising the C-terminus of the protein, Overexpression of N-terminal mutations disturbs mitosis and produces elongated cells , Using a PCR approach, we isolated a putative homologue of Prp4 from human and mouse cells, The mammalian kinase domain is 53% identical to the kinase domain of Prp4. The short N-terminal domains share <20% id entical amino acids, but contain conserved motifs, A fusion protein co nsisting of the N-terminal region from S.pombe followed by the mammali an kinase domain complements a temperature-sensitive prp4 mutation of S.pombe. Prp4 and the recombinant yeast/mouse protein kinase phosphory late the human SR splicing factor ASF/SF2 in vitro in its RS domain.