title: Small ubiquitin-related modifier ligase activity of Mms21 is required for maintenance of chromosome integrity during the unperturbed mitotic cell division cycle in Saccharomyces cerevisiae.
abstract: The SUMO ligase activity of Mms21/Nse2, a conserved member of the Smc5/6 complex, is required for resisting extrinsically induced genotoxic stress. We report that the Mms21 SUMO ligase activity is also required during the unchallenged mitotic cell cycle in Saccharomyces cerevisiae. SUMO ligase-defective cells were slow growing and spontaneously incurred DNA damage. These cells required caffeine-sensitive Mec1 kinase-dependent checkpoint signaling for survival even in the absence of extrinsically induced genotoxic stress. SUMO ligase-defective cells were sensitive to replication stress and displayed synthetic growth defects with DNA damage checkpoint-defective mutants such as mec1, rad9, and rad24. MMS21 SUMO ligase and mediator of replication checkpoint 1 gene (MRC1) were epistatic with respect to hydroxyurea-induced replication stress or methyl methanesulfonate-induced DNA damage sensitivity. Subjecting Mms21 SUMO ligase-deficient cells to transient replication stress resulted in enhancement of cell cycle progression defects such as mitotic delay and accumulation of hyperploid cells. Consistent with the spontaneous activation of the DNA damage checkpoint pathway observed in the Mms21-mediated sumoylation-deficient cells, enhanced frequency of chromosome breakage and loss was detected in these mutant cells. A mutation in the conserved cysteine 221 that is engaged in coordination of the zinc ion in Loop 2 of the Mms21 SPL-RING E3 ligase catalytic domain resulted in strong replication stress sensitivity and also conferred slow growth and Mec1 dependence to unchallenged mitotically dividing cells. Our findings establish Mms21-mediated sumoylation as a determinant of cell cycle progression and maintenance of chromosome integrity during the unperturbed mitotic cell division cycle in budding yeast.
authors.affiliation: Department of Biochemistry, Indian Institute of Science, C. V. Raman Avenue, Bangalore, Karnataka 560012, India.
authors.forename: Ragini
authors.initials: R
authors.lastname: Rai
authors.forename: Satya P M V
authors.initials: SP
authors.lastname: Varma
authors.forename: Nikhil
authors.initials: N
authors.lastname: Shinde
authors.forename: Shilpa
authors.initials: S
authors.lastname: Ghosh
authors.forename: Srikala P
authors.initials: SP
authors.lastname: Kumaran
authors.forename: Geena
authors.initials: G
authors.lastname: Skariah
authors.forename: Shikha
authors.initials: S
authors.lastname: Laloraya
mesh_terms: D000483:Alleles; D000595:Amino Acid Sequence; D020134:Catalytic Domain; D002875:Chromosomes / Q000378:metabolism*; D018244:Chromosomes, Artificial, Yeast; D018450:Disease Progression; D004843:Epistasis, Genetic; D015966:Gene Expression Regulation, Fungal; D008938:Mitosis; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D025842:SUMO-1 Protein / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D016615:Telomere / Q000648:ultrastructure; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry
chemical_list: C500948:Mms21 protein, S cerevisiae; D025842:SUMO-1 Protein; D029701:Saccharomyces cerevisiae Proteins; D044767:Ubiquitin-Protein Ligases