HRR25, a Putative Protein Kinase from Budding Yeast: Association with Repair of Damaged DNA

Abstract

In simple eukaryotes, protein kinases regulate mitotic and meiotic cell cycles, the response to polypeptide pheromones, and the initiation of nuclear DNA synthesis. The protein HRR25 from the budding yeast Saccharomyces cerevisiae was defined by the mutation hrr25-1. This mutation resulted in sensitivity to continuous expression of the HO double-strand endonuclease, to methyl methanesulfonate, and to x-irradiation. Homozygotes of hrr25-1 were unable to sporulate and disruption and deletion of HRR25 interfered with mitotic and meiotic cell division. Sequence analysis revealed two distinctive regions in the protein. The NH2-terminus of HRR25 contains the hallmark features of protein kinases, whereas the COOH-terminus is rich in proline and glutamine. Mutations in HRR25 at conserved residues found in all protein kinases inactivated the gene, and these mutants exhibited the hrr25 null phenotypes. Taken together, the hrr25 mutant phenotypes and the features of the gene product indicate that HRR25 is a distinctive member of the protein kinase superfamily.

Two genes in Saccharomyces cerevisiae encode a membrane-bound form of casein kinase-1.

“…The closest matches were with three mammalian CK1 isozymes (51-56% identity) (Rowles et al, 1991) and with HRR25, a protein kinase associated with repair of damaged DNA in S. cerevisiae (50-52% identity) (Hoekstra et al, 1991). Despite the similarity in nomenclature, CK1 is structurally unrelated to the catalytic (a) subunit of casein kinase-2 (Padmanabha et al, 1990).…”

p53 is phosphorylated in vitro and in vivo by the delta and epsilon isoforms of casein kinase 1 and enhances the level of casein kinase 1 delta in response to topoisomerase-directed drugs

“…CK1 isoforms are thought to be involved in the regulation of DNA repair and chromosomal segregation. For example, the S. cerevisiae hrr 25 gene encodes a protein kinase with striking similarity to CK1 family members: hrr 25 mutants show sensitivity to DNA damage and have defects in nuclear segregation and meiotic division (Hoekstra et al, 1991). Two genes in S. pombe, hhp 1 and hhp 2, may play similar roles to hrr 25 and deletion of these genes generates large cells containing multiple nuclei (i.e.…”

“…Our ®nding that p53 is preferentially phosphorylated by a CK1-like enzyme, which is separable from CK1a by a nity chromatography, suggests that p53 is phosphorylated in the cell by a CK1 isoform or a highly related kinase . Moreover, the potential interaction of p53 with members of the CK1 family is of striking interest since CK1 family members play an integral role in resistance to radiation and DNA damage in yeasts and Drosophila (Dhillon and Hoekstra, 1994;Hoekstra et al, 1991). Finally, our recent observation that p53 N-terminus-targeted protein kinase (p53NK) activity can be stimulated by anti-tumour drugs which elicit DNA damage (Knippschild et al, 1996) makes the identi®cation of this kinase(s) and characterisation of its interaction with p53 a major goal in understanding the mechanisms which activate and control p53 function.…”

Arabidopsis thaliana mutants altered in homologous recombination

“…Yeast mutations with phenotypes of DNA-damage hypersensitivity have been isolated recently that map to genes of signaling kinases. For example, a mutation of the HRR25 kinase gene results in increased sensitivity to x-ray radiation and MMS, reduced sporulation and spore viability, as well as decreased mitotic recombination (35). A mutation in the regulatory protein kinase C (PKC1) also inf luences rates of mitotic recombination (36).…”