Involvement of rhp23, a Schizosaccharomyces pombe homolog of the human HHR23A and Saccharomyces cerevisiae RAD23 nucleotide excision repair genes, in cell cycle control and protein ubiquitination.
A functional homolog (rhp23) of human HHR23A and Saccharomyces cerevisiae RAD23 was cloned from the fission yeast Schizosaccharomyces pombe and characterized. Consistent with the role of Rad23 homologs in nucleotide excision repair, rhp23 mutant cells are moderately sensitive to UV light but demonstrate wild-type resistance to gamma-rays and hydroxyurea. Expression of the rhp23, RAD23 or HHR23A cDNA restores UV resistance to the mutant, indicating that rhp23 is a functional homolog of the human and S.cerevisiae genes. The rhp23::ura4 mutation also causes a delay in the G2 phase of the cell cycle which is corrected when rhp23, RAD23 or HHR23A cDNA is expressed. Rhp23 is present throughout the cell but is located predominantly in the nucleus, and the nuclear levels of Rhp23 decrease around the time of S phase in the cell cycle. Rhp23 is ubiquitinated at low levels, but overexpression of the rhp23 cDNA induces a large increase in ubiquitination of other proteins. Consistent with a role in protein ubiquitination, Rhp23 binds ubiquitin, as determined by two-hybrid analysis. Thus, the rhp23 gene plays a role not only in nucleotide excision repair but also in cell cycle regulation and the ubiquitination pathways.
Elder
Robert T
RT
Children's Memorial Institute for Education and Research, Departments of Pediatrics and Microbiology-Immunology, Northwestern University Medical School, 2430 North Halstead Street, 218, Chicago, IL 60614, USA.
Song
Xiang-qian
XQ
Chen
Mingzhong
M
Hopkins
Kevin M
KM
Lieberman
Howard B
HB
Zhao
Yuqi
Y
D000595:Amino Acid Sequence; D002453:Cell Cycle; D002467:Cell Nucleus / Q000378:metabolism; D003001:Cloning, Molecular; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016195:G2 Phase; D005720:Gamma Rays; D005816:Genetic Complementation Test; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D021381:Protein Transport; D011836:Radiation Tolerance / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism*; D014466:Ultraviolet Rays
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C490846:RAD23 protein, S cerevisiae; C490845:RHP23 protein, S pombe; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D025801:Ubiquitin; C086985:RAD23A protein, human; D045643:DNA Repair Enzymes; D006918:Hydroxyurea