Abstract
Structural maintenance of chromosomes (SMC) proteins play central roles in chromosome organization and dynamics. They have been classified into six subtypes, termed SMC1 to SMC6, and function as heterodimer components of large protein complexes that also include several non-SMC proteins. The SMC2-SMC4 and SMC1-SMC3 complexes are also known as condensin and cohesin, respectively, but the recently identified SMC5 and SMC6 complex is less well characterized. Here, we report that NSE1 from Saccharomyces cerevisiae encodes a novel non-SMC component of the SMC5(Yol034wp)-SMC6(Rhc18p) complex corresponding to the 2-3-MDa molecular mass. Nse1p is essential for cell proliferation and localizes primarily in the nucleus. nse1 mutants are highly sensitive to DNA-damaging treatments and exhibit abnormal cellular morphologies, suggesting aberrant mitosis as a terminal morphological phenotype. These results are consistent with the reported features of the Schizosaccharomyces pombe SMC6 gene, rad18, which is thought to be involved in recombinational DNA repair. We conclude that Nse1p and the SMC5-SMC6 heterodimer together form a high molecular mass complex that is conserved in eukaryotes and required for both DNA repair and proliferation.
Highlights
The superfamily structural maintenance of chromosomes (SMC)1 consists of proteins with important functions in chromosome maintenance
We report that NSE1 from Saccharomyces cerevisiae encodes a novel non-Structural maintenance of chromosomes (SMC) component of the SMC5(Yol034wp)SMC6(Rhc18p) complex corresponding to the 2–3-MDa molecular mass
We conclude that Nse1p and the SMC5-SMC6 heterodimer together form a high molecular mass complex that is conserved in eukaryotes and required for both DNA repair and proliferation
Summary
MATa/␣ ura3–52/ura HIS3/his3⌬200 leu2⌬1/leu2⌬1 LYS2/lys2⌬202 TRP1/trp1⌬63 MATa/␣ ura3–52/ura his3⌬200/HIS3 leu2⌬1/LEU2 TRP1/trp1⌬63 nse1⌬ϻkanMX4/NSE1 MATa his3⌬200 MATa ura his3⌬200 nse1ϻLEU2 lys2⌬202 [pRS316/NSE1] MAT␣ ura his3⌬200 leu2⌬1 trp1⌬63 nse1⌬ϻkanMX4 [pAML10/HA-NSE1] MAT␣ ura his3⌬200 leu2⌬1 trp1⌬63 nse1⌬ϻkanMX4 [pAML10/NSE1] MATa ura smc6⌬ϻHIS3 leu2⌬1 lys2⌬202 trp1⌬63 nse1⌬ϻkanMX4 [pAML10/HA-NSE1] [pRS314/FLAG-SMC6] MATa ura smc5⌬ϻHIS3 leu2⌬1 lys2⌬202 trp1⌬63 nse1⌬ϻkanMX4 [pAML10/HA-NSE1] [pRS314/SMC5-FLAG] MATa ura his3⌬200 nse1ϻLEU2 lys2⌬202 [pRS313/NSE1] MATa ura his3⌬200 nse1ϻLEU2 lys2⌬202 [pRS313/nse1-14] MATa ura his3⌬200 nse1ϻLEU2 lys2⌬202 [pRS313/nse1-16] MAT␣ ura his3⌬200 leu2⌬1 trp1⌬63 nse1⌬ϻkanMX4 [pGAL1/NSE1] MAT␣ ura his3⌬200 leu2⌬1 trp1⌬63 nse1⌬ϻkanMX4 [pGAL1/nse1–20]. We examine the function of YLR007w, a previously uncharacterized S. cerevisiae gene that was obtained from one of a collection of yeast mutants exhibiting abnormal nuclear morphology [20, 29]. Our results strongly suggest that the product of YLR007w associates with Yol034wp and Rhc18p, which are predicted to be the S. cerevisiae orthologues SMC5 and SMC6, respectively, to form a high molecular mass complex. We found that ylr007w mutant strains exhibit phenotypes resembling those of S. pombe rad mutants, including enhanced sensitivity to DNAdamaging treatments. We conclude that YLR007w encodes a non-SMC component of the SMC5-SMC6 high molecular mass complex, and propose that this gene be called NSE1 (non-SMC element 1)
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