Premature Chromatin Condensation Induced by Loss of RCC1 Is Inhibited by GTP- and GTPγS-Ran, but Not GDP-Ran

Tomoyuki Ohba, Takashi Seki, Yoshiaki Azuma, Takeharu Nishimoto
1996 Journal of Biological Chemistry  
RCC1 is a guanine nucleotide exchanging factor acting on nuclear G protein Ran. Premature chromatin condensation occurs in the temperature-sensitive rcc1 ؊ mutant of the BHK21 cell line, tsBN2, at the restrictive temperature. This observation can be explained if the premature activation of MPF is normally inhibited by GTP-Ran. In the absence of RCC1, GDP-Ran predominates, resulting in MPF activation. However, experiments with Ran mutants to determine whether GTP-or GDP-Ran prevents activation
more » ... MPF have yielded conflicting results. In order to clarify this point, we have microinjected nucleotide-bound Ran, instead of mutated Ran, into the nuclei of tsBN2 cells treated to reduce RCC1-mediated guanine nucleotide exchange. GTP-Ran, GTP␥S-Ran, and GDP-Ran all inhibited chromatin condensation. However, the inhibition of chromatin condensation by GDP-Ran could be completely abolished by co-injection with GDP, but not GTP. Thus, we conclude that GTP-Ran blocks the activation of MPF and that hydrolysis of GTP is not required to prevent MPF activation.
doi:10.1074/jbc.271.25.14665 pmid:8663347 fatcat:rrhmznvgfzcqljoduqv3iyb3ey