‡Department of Anatomy, Histology, Forensic Medicine and Orthopedics, Section of Histology and Embryology, Faculty of Pharmacy and Medicine, "Sapienza" University Rome, V.le Regina Elena 324, 00161 Rome, Italy.
Biochem J. 2013 Feb 1;449(3):623-30. doi: 10.1042/BJ20121429.
Ctcf (CCCTC-binding factor) directly induces Parp [poly(ADP-ribose) polymerase] 1 activity and its PARylation [poly(ADPribosyl)ation] in the absence of DNA damage. Ctcf, in turn, is a substrate for this post-synthetic modification and as such it is covalently and non-covalently modified by PARs (ADP-ribose polymers). Moreover, PARylation is able to protect certain DNA regions bound by Ctcf from DNA methylation. We recently reported that de novo methylation of Ctcf target sequences due to overexpression of Parg [poly(ADP-ribose)glycohydrolase] induces loss of Ctcf binding. Considering this, we investigate to what extent PARP activity is able to affect nuclear distribution of Ctcf in the present study. Notably, Ctcf lost its diffuse nuclear localization following PAR (ADP-ribose polymer) depletion and accumulated at the periphery of the nucleus where it was linked with nuclear pore complex proteins remaining external to the perinuclear Lamin B1 ring. We demonstrated that PAR depletion-dependent perinuclear localization of Ctcf was due to its blockage from entering the nucleus. Besides Ctcf nuclear delocalization, the outcome of PAR depletion led to changes in chromatin architecture. Immunofluorescence analyses indicated DNA redistribution, a generalized genomic hypermethylation and an increase of inactive compared with active chromatin marks in Parg-overexpressing or Ctcf-silenced cells. Together these results underline the importance of the cross-talk between Parp1 and Ctcf in the maintenance of nuclear organization.
CTCF（CCCTC 结合因子）在没有 DNA 损伤的情况下直接诱导 PARP1（多聚（ADP-核糖）聚合酶）1 的活性及其 PAR 化（多聚（ADP 核糖）化）。反过来，CTCF 又是这种翻译后修饰的底物，因此它被 PAR（ADP-核糖聚合物）共价和非共价修饰。此外，PAR 化能够保护由 CTCF 结合的某些 DNA 区域免受 DNA 甲基化。我们最近报道，由于 Parg（多聚（ADP-核糖）糖水解酶）的过表达导致 CTCF 靶序列的从头甲基化，导致 CTCF 结合的丧失。考虑到这一点，我们在本研究中研究了 PARP 活性在多大程度上能够影响 CTCF 的核分布。值得注意的是，PAR（ADP-核糖聚合物）耗尽后，CTCF 失去了其弥散的核定位，并在核的外围积累，在那里它与核孔复合物蛋白结合，这些蛋白位于核周 Lamin B1 环之外。我们证明，PAR 耗竭依赖性的 CTCF 核周定位是由于其被阻止进入核内。除了 CTCF 的核去定位外，PAR 耗竭的结果还导致染色质结构发生变化。免疫荧光分析表明，在 Parg 过表达或 CTCF 沉默的细胞中，DNA 重新分布，全基因组超甲基化以及与活性染色质标记相比，无活性染色质标记增加。这些结果共同强调了 PARP1 和 CTCF 之间的相互作用在维持核组织中的重要性。
