Comment in:

Cell. 2007 Jan 12;128(1):20-1.

PICH, a centromere-associated SNF2 family ATPase, is regulated by Plk1 and required for the spindle checkpoint.

Department of Cell Biology, Max Planck Institute of Biochemistry, D-82152 Martinsried, Germany.

We identify PICH (Plk1-interacting checkpoint "helicase"), a member of the SNF2 ATPase family, as an interaction partner and substrate of Plk1. Following phosphorylation of PICH on the Cdk1 site T1063, Plk1 is recruited to PICH and controls its localization. Starting in prometaphase, PICH accumulates at kinetochores and inner centromeres. Moreover, it decorates threads that form during metaphase before increasing in length and progressively diminishing during anaphase. PICH-positive threads connect sister kinetochores and are dependent on tension, sensitive to DNase, and exacerbated in response to premature loss of cohesins or inhibition of topoisomerase II, suggesting that they represent stretched centromeric chromatin. Depletion of PICH causes the selective loss of Mad2 from kinetochores and completely abrogates the spindle checkpoint, resulting in massive chromosome missegregation. These data identify PICH as a novel essential component of checkpoint signaling. We propose that PICH binds to catenated centromere-related DNA to monitor tension developing between sister kinetochores.

PMID: 17218258 [PubMed - indexed for MEDLINE]

Targeting Plk1 to chromosome arms and regulating chromosome compaction by the PICH ATPase.

Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.

During mitosis, chromosomes undergo dynamic structural changes that include condensation of chromosomes-the formation of individual compact chromosomes necessary for faithful segregation of sister chromatids in anaphase. Polo-like kinase 1 (Plk1) regulates multiple mitotic events by binding to targeting factors at different mitotic structures in a phosphorylation dependent manner. In this study, we report the identification of a putative ATPase that targets Plk1 to chromosome arms during mitosis. PICH (Plk1-interacting checkpoint "helicase") displays a temporal localization on chromosome arms and kinetochores during early mitosis. Interaction with PICH recruits Plk1 to chromosome arms and disruption of this interaction abolishes Plk1 localization on chromosome arms. Moreover, depletion of PICH or overexpression of PICH mutant that is defective in Plk1 binding or ATP binding causes defects in mitotic chromosome compaction, formation of anaphase bridge and cytokinesis failure. We provide data to show that both PICH phosphorylation and its ATPase activity are required for mitotic chromosome compaction. Our study provides a mechanism for targeting Plk1 to chromosome arms and suggests that the PICH ATPase activity is important for the regulation of mitotic chromosome architecture.

PMID: 18418076 [PubMed - indexed for MEDLINE]

Ercc6l, a gene of SNF2 family, may play a role in the teratogenic action of alcohol.

Laboratory of Molecular Toxicology & Developmental Molecular Biology, Department of Nutrition & Food Hygiene, School of Public Health, Peking University, Beijing 100083, China.

The expression profile of a newly identified mouse nucleotide excision repair (NER) gene, Ercc6l, was investigated in a mouse model of fetal alcohol syndrome (FAS). In test 1, whole-mount in situ hybridization showed Ercc6l expressed mainly in the neural tube and heart of 10.5-day embryo. However, the expressions in both of the two organs were significantly down regulated after in uterus alcohol exposure from embryonic day (ED) 6-10, which was in accordance with the result of semi-quantitative RT-PCR. In test 2, the dams were given alcohol intragastrically from ED 6-15, and Northern blot of Ercc6l mRNA was carried out with five major embryo organs on ED 15.5, which were heart, brain, kidney, liver and lung. Ercc6l expression in 15.5-day embryonic brain and heart, which are the most commonly affected organs of FAS, were both decreased by alcohol exposure. The expressions in the other three organs were unaffected. From the results, we considered that Ercc6l might play a role in the teratogenic action of alcohol.

PMID: 15917148 [PubMed - indexed for MEDLINE]

Depletion of topoisomerase IIalpha leads to shortening of the metaphase interkinetochore distance and abnormal persistence of PICH-coated anaphase threads.

Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, UK.

Topoisomerase II (topo II) is a major component of mitotic chromosomes, and its unique decatenating activity has been implicated in many aspects of chromosome dynamics, of which chromosome segregation is the most seriously affected by loss of topo II activity in living cells. There is considerable evidence that topo II plays a role at the centromere including: the centromere-specific accumulation of topo II protein; cytogenetic/molecular mapping of the catalytic activity of topo II to active centromeres; the influence of sumoylated topo II on sister centromere cohesion; and its involvement in the activation of a Mad2-dependent spindle checkpoint. By using a human cell line with a conditional-lethal mutation in the gene encoding DNA topoisomerase IIalpha, we find that depletion of topo IIalpha, while leading to a disorganised metaphase plate, does not have any overt effect on general assembly of kinetochores. Fluorescence in situ hybridisation suggested that centromeres segregate normally, most segregation errors being chromatin bridges involving longer chromosome arms. Strikingly, a linear human X centromere-based minichromosome also displayed a significantly increased rate of missegregation. This sensitivity to depletion of topo IIalpha might be linked to structural alterations within the centromere domain, as indicated by a significant shortening of the distance across metaphase sister centromeres and the abnormal persistence of PICH-coated connections between segregating chromatids.

PMID: 17956945 [PubMed - indexed for MEDLINE]