Chang Fiona T M, Chan F Lyn, R McGhie James D, Udugama Maheshi, Mayne Lynne, Collas Philippe, Mann Jeffrey R, Wong Lee H
Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
Institute of Basic Medical Sciences, and Norwegian Center for Stem Cell Research, Faculty of Medicine, University of Oslo, Oslo 0317, Norway.
Nucleic Acids Res. 2015 Mar 11;43(5):2603-14. doi: 10.1093/nar/gkv104. Epub 2015 Feb 17.
Human ALT cancers show high mutation rates in ATRX and DAXX. Although it is well known that the absence of ATRX/DAXX disrupts H3.3 deposition at heterochromatin, its impact on H3.3 deposition and post-translational modification in the global genome remains unclear. Here, we explore the dynamics of phosphorylated H3.3 serine 31 (H3.3S31ph) in human ALT cancer cells. While H3.3S31ph is found only at pericentric satellite DNA repeats during mitosis in most somatic human cells, a high level of H3.3S31ph is detected on the entire chromosome in ALT cells, attributable to an elevated CHK1 activity in these cells. Drug inhibition of CHK1 activity during mitosis and expression of mutant H3.3S31A in these ALT cells result in a decrease in H3.3S31ph levels accompanied with increased levels of phosphorylated H2AX serine 139 on chromosome arms and at the telomeres. Furthermore, the inhibition of CHK1 activity in these cells also reduces cell viability. Our findings suggest a novel role of CHK1 as an H3.3S31 kinase, and that CHK1-mediated H3.3S31ph plays an important role in the maintenance of chromatin integrity and cell survival in ALT cancer cells.
人类端粒酶替代途径（ALT）相关癌症在ATRX和DAXX基因中显示出高突变率。尽管众所周知，ATRX/DAXX的缺失会破坏异染色质上H3.3的沉积，但其对全基因组中H3.3沉积和翻译后修饰的影响仍不清楚。在此，我们探索了人类ALT癌细胞中磷酸化H3.3丝氨酸31（H3.3S31ph）的动态变化。在大多数人体体细胞有丝分裂期间，H3.3S31ph仅在着丝粒卫星DNA重复序列处被发现，而在ALT细胞的整个染色体上检测到高水平的H3.3S31ph，这归因于这些细胞中CHK1活性的升高。在有丝分裂期间对CHK1活性进行药物抑制以及在这些ALT细胞中表达突变型H3.3S31A，会导致H3.3S31ph水平降低，同时染色体臂和端粒上磷酸化H2AX丝氨酸139的水平升高。此外，抑制这些细胞中的CHK1活性也会降低细胞活力。我们的研究结果表明CHK1作为H3.3S31激酶具有新的作用，并且CHK1介导的H3.3S31ph在ALT癌细胞的染色质完整性维持和细胞存活中起重要作用。
