Schizosaccharomyces pombe Snf2SR, a novel SNF2 family protein, interacts with Ran GTPase and modulates both RanGEF and RanGAP activities.
Snf2SR, a suppressor of rna1(ts), which is a temperature-sensitive mutation in Schizosaccharomyces pombe RanGAP (GTPase activating protein), possesses both the SNF2 and the helicase domains conserved in the chromatin remodeling SNF2 ATPase/helicase protein family. We have now clarified a function of Snf2SR. Snf2SR indeed showed DNA-stimulated ATPase activity, proving that it is a member of the SNF2 ATPase/helicase family. Consistent with this role, Snf2SR was localized in the nucleus and cell fractionation analysis revealed that Snf2SR was tightly associated with the nuclear matrix. The disruption of snf2SR(+) was detrimental for a cell proliferation of S. pombe. Snf2SR that did not enhance RanGAP activity by itself, but abolished histone-H3-mediated RanGAP inhibition, as previously reported for the histone H3 methyltransferase, Clr4, another rna1(ts) suppressor. In contrast to Clr4, Snf2SR directly bound to the GDP-bound form of the S. pombe Ran homologue Spi1 and enhanced the nucleotide exchange activity of Pim1, the S. pombe RanGEF (guanine nucleotide exchange factor). Over-expression of Spi1-G18V, a Ran GTPase mutant fixed in the GTP-bound form, was lethal to S. pombe Deltasnf2SR. Together, our results indicate that Snf2SR is involved in the Ran GTPase cycle in vivo.
Ohba
Tomoyuki
T
Department of Molecular Biology, Graduate School of Medical Science, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
Nishijima
Hitoshi
H
Nishitani
Hideo
H
Nishimoto
Takeharu
T
D000251:Adenosine Triphosphatases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000737:chemistry; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D017353:Gene Deletion; D006657:Histones / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000378:metabolism*
D000251:Adenosine Triphosphatases; D002868:Chromosomal Proteins, Non-Histone; D006657:Histones; D029702:Schizosaccharomyces pombe Proteins; D020931:ran GTP-Binding Protein; C559589:Fft3 protein, S pombe