Functional analysis of the fission yeast Prp4 protein kinase involved in pre-mRNA splicing and isolation of a putative mammalian homologue

The prp4 gene of Schizosaccharomyces pombe encodes a protein kinase, A physiological substrate is not yet known, A mutational analysis of prp4 revealed that the protein consists of a short N-terminal domain, containing several essential motifs, which is followed by the kinase catalytic 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% identical amino acids, but contain conserved motifs, A fusion protein consisting of the N-terminal region from S.pombe followed by the mammalian kinase domain complements a temperature-sensitive prp4 mutation of S.pombe. Prp4 and the recombinant yeast/mouse protein kinase phosphorylate the human SR splicing factor ASF/SF2 in vitro in its RS domain.