title: The plant homeodomain fingers of fission yeast Msc1 exhibit E3 ubiquitin ligase activity.
abstract: The DNA damage checkpoint pathway governs how cells regulate cell cycle progression in response to DNA damage. A screen for suppressors of a fission yeast chk1 mutant defective in the checkpoint pathway identified a novel Schizosaccharomyces pombe protein, Msc1. Msc1 contains 3 plant homeodomain (PHD) finger motifs, characteristically defined by a C4HC3 consensus similar to RING finger domains. PHD finger domains in viral proteins and in the cellular protein kinase MEKK1 (mitogen-activated protein kinase/extracellular signal-regulated kinase kinase kinase 1) have been implicated as ubiquitin E3 protein ligases that affect protein stability. The close structural relationship of PHD fingers to RING fingers suggests that other PHD domain-containing proteins might share this activity. We show that each of the three PHD fingers of Msc1 can act as ubiquitin E3 ligases, reporting for the first time that PHD fingers from a nuclear protein exhibit E3 ubiquitin ligase activity. The function of the PHD fingers of Msc1 is needed to rescue the DNA damage sensitivity of a chk1Delta strain. Msc1 co-precipitates Rhp6, the S. pombe homologue of the human ubiquitin-conjugating enzyme Ubc2. Strikingly, deletion of msc1 confers complete suppression of the slow growth phenotype, UV and hydroxyurea sensitivities of an rhp6 deletion strain and restores deficient histone H3 methylation observed in the rhp6Delta mutant. We speculate that the target of the E3 ubiquitin ligase activity of Msc1 is likely to be a chromatin-associated protein.
authors: Department of Pharmacology, University of Medicine and Dentistry of New Jersey (UMDNJ)-Robert Wood Johnson Medical School and the Joint Graduate Program in Cellular and Molecular Pharmacology, UMDNJ-Graduate School of Biomedical Sciences and Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854.
authors: Barbara E
authors: BE
authors: Dul
authors: Department of Pharmacology, University of Medicine and Dentistry of New Jersey (UMDNJ)-Robert Wood Johnson Medical School and the Joint Graduate Program in Cellular and Molecular Pharmacology, UMDNJ-Graduate School of Biomedical Sciences and Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854. Electronic address: walworna@umdnj.edu.
authors: Nancy C
authors: NC
authors: Walworth
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002453:Cell Cycle; D000071877:Checkpoint Kinase 1; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000737:chemistry*; D017353:Gene Deletion; D008969:Molecular Sequence Data; D011494:Protein Kinases / Q000737:chemistry; D012568:Schizosaccharomyces / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry*; D013696:Temperature; D025801:Ubiquitin / Q000737:chemistry; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry*; D014466:Ultraviolet Rays
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; C486643:Msc1 protein, S pombe; D029702:Schizosaccharomyces pombe Proteins; D025801:Ubiquitin; D044767:Ubiquitin-Protein Ligases; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605873:Chk1 protein, S pombe