Azuma Yoshiaki, Arnaoutov Alexei, Anan Tadashi, Dasso Mary
Laboratory of Gene Regulation and Development, NICHD, NIH, Bethesda, MD 20892-5431, USA.
EMBO J. 2005 Jun 15;24(12):2172-82. doi: 10.1038/sj.emboj.7600700. Epub 2005 Jun 2.
Here we show that the PIASy protein is specifically required for mitotic modification of Topoisomerase-II by SUMO-2 conjugation in Xenopus egg extracts. PIASy was unique among the PIAS family members in its capacity to bind mitotic chromosomes and recruit Ubc9 onto chromatin. These properties were essential, since PIASy mutants that did not bind chromatin or failed to recruit Ubc9 were functionally inactive. We observed that PIASy depletion eliminated essentially all chromosomal accumulation of EGFP-SUMO-2-conjugated species, suggesting that it is the primary E3-like factor for mitotic chromosomal substrates of SUMO-2. PIASy-dependent SUMO-2-conjugated species were highly concentrated on the inner centromere, and inhibition of PIASy blocked anaphase sister chromatid segregation in egg extracts. Taken together, our observations suggest that PIASy is a critical regulator of mitotic SUMO-2 conjugation for Topoisomerase-II and other chromosomal substrates, and that its activity may have particular relevance for centromeric functions required for proper chromosome segregation.
我们在此表明，在非洲爪蟾卵提取物中，PIASy蛋白是拓扑异构酶II通过SUMO-2共轭进行有丝分裂修饰所特别需要的。PIASy在PIAS家族成员中具有独特之处，它能够结合有丝分裂染色体并将Ubc9募集到染色质上。这些特性至关重要，因为无法结合染色质或未能募集Ubc9的PIASy突变体在功能上是无活性的。我们观察到，PIASy的缺失基本上消除了所有与EGFP-SUMO-2共轭的物种在染色体上的积累，这表明它是SUMO-2有丝分裂染色体底物的主要类E3因子。依赖PIASy的SUMO-2共轭物种高度集中在内着丝粒上，并且对PIASy的抑制会阻断卵提取物中的后期姐妹染色单体分离。综上所述，我们的观察结果表明，PIASy是拓扑异构酶II和其他染色体底物有丝分裂SUMO-2共轭的关键调节因子，并且其活性可能与正确染色体分离所需的着丝粒功能特别相关。
