Hilton Benjamin A, Liu Ji, Cartwright Brian M, Liu Yiyong, Breitman Maya, Wang Youjie, Jones Rowdy, Tang Hui, Rusinol Antonio, Musich Phillip R, Zou Yue
Department of Biomedical Sciences, J. H. Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee, USA.
Department of Biochemistry and Molecular Biology, West China Center of Medical Sciences, Sichuan University, Chengdu, China.
FASEB J. 2017 Sep;31(9):3882-3893. doi: 10.1096/fj.201700014R. Epub 2017 May 17.
Hutchinson-Gilford progeria syndrome (HGPS) is a rare genetic disorder that is caused by a point mutation in the gene, resulting in production of a truncated farnesylated-prelamin A protein (progerin). We previously reported that XPA mislocalized to the progerin-induced DNA double-strand break (DSB) sites, blocking DSB repair, which led to DSB accumulation, DNA damage responses, and early replication arrest in HGPS. In this study, the XPA mislocalization to DSBs occurred at stalled or collapsed replication forks, concurrent with a significant loss of PCNA at the forks, whereas PCNA efficiently bound to progerin. This PCNA sequestration likely exposed ds-ssDNA junctions at replication forks for XPA binding. Depletion of XPA or progerin each significantly restored PCNA at replication forks. Our results suggest that although PCNA is much more competitive than XPA in binding replication forks, PCNA sequestration by progerin may shift the equilibrium to favor XPA binding. Furthermore, we demonstrated that progerin-induced apoptosis could be rescued by XPA, suggesting that XPA-replication fork binding may prevent apoptosis in HGPS cells. Our results propose a mechanism for progerin-induced genome instability and accelerated replicative senescence in HGPS.-Hilton, B. A., Liu, J., Cartwright, B. M., Liu, Y., Breitman, M., Wang, Y., Jones, R., Tang, H., Rusinol, A., Musich, P. R., Zou, Y. Progerin sequestration of PCNA promotes replication fork collapse and mislocalization of XPA in laminopathy-related progeroid syndromes.
哈钦森-吉尔福德早衰综合征（HGPS）是一种罕见的遗传性疾病，由基因中的一个点突变引起，导致产生截短的法尼基化前层粘连蛋白A蛋白（早老素）。我们之前报道过，XPA错误定位于早老素诱导的DNA双链断裂（DSB）位点，阻碍了DSB修复，这导致了DSB积累、DNA损伤反应以及HGPS中的早期复制停滞。在本研究中，XPA向DSB的错误定位发生在停滞或崩溃的复制叉处，同时叉处的增殖细胞核抗原（PCNA）显著丢失，而PCNA有效地与早老素结合。这种PCNA隔离可能会暴露复制叉处的双链-单链DNA连接点以供XPA结合。XPA或早老素的缺失均显著恢复了复制叉处的PCNA。我们的结果表明，尽管PCNA在结合复制叉方面比XPA更具竞争力，但早老素对PCNA的隔离可能会使平衡向有利于XPA结合的方向转变。此外，我们证明早老素诱导的细胞凋亡可以被XPA挽救，这表明XPA与复制叉的结合可能会防止HGPS细胞中的细胞凋亡。我们的结果提出了一种早老素诱导HGPS基因组不稳定和加速复制性衰老的机制。-希尔顿，B.A.，刘，J.，卡特赖特，B.M.，刘，Y.，布赖特曼，M.，王，Y.，琼斯，R.，唐，H.，鲁西诺尔，A.，穆西奇，P.R.，邹，Y.早老素对PCNA的隔离促进层粘连蛋白病相关早衰综合征中复制叉崩溃和XPA错误定位。
