Nusinow Dmitri A, Hernández-Muñoz Inmaculada, Fazzio Thomas G, Shah Girish M, Kraus W Lee, Panning Barbara
Department of Biochemistry and Biophysics, University of California, San Francisco, California 94158, USA.
J Biol Chem. 2007 Apr 27;282(17):12851-9. doi: 10.1074/jbc.M610502200. Epub 2007 Feb 23.
Poly(ADP-ribose) polymerase 1 (PARP-1) is a nuclear enzyme that is involved in modulating chromatin structure, regulation of gene expression, and sensing DNA damage. Here, we report that PARP-1 enzymatic activity is inhibited by macroH2A, a vertebrate histone H2A variant that is enriched on facultative heterochromatin. MacroH2A family members have a large C-terminal non-histone domain (NHD) and H2A-like histone domain. MacroH2A1.2 and PARP-1 interact in vivo and in vitro via the NHD. The NHD of each macroH2A family member was sufficient to inhibit PARP-1 enzymatic activity in vitro. The NHD of macroH2A1.2 was a mixed inhibitor of PARP-1 catalytic activity, with affects on both catalytic activity and the substrate binding affinity of PARP-1. Depletion of PARP-1 by RNA interference caused reactivation of a reporter gene on the inactive X chromosome, demonstrating that PARP-1 participates in the maintenance of silencing. These results suggest that one function of macroH2A in gene silencing is to inhibit PARP-1 enzymatic activity, and this may affect PARP-1 association with chromatin.
聚（ADP - 核糖）聚合酶1（PARP - 1）是一种核酶，参与调节染色质结构、基因表达调控以及感知DNA损伤。在此，我们报道PARP - 1的酶活性受到macroH2A的抑制，macroH2A是一种在兼性异染色质上富集的脊椎动物组蛋白H2A变体。MacroH2A家族成员具有一个大的C末端非组蛋白结构域（NHD）和H2A样组蛋白结构域。MacroH2A1.2和PARP - 1在体内和体外通过NHD相互作用。每个macroH2A家族成员的NHD在体外足以抑制PARP - 1的酶活性。MacroH2A1.2的NHD是PARP - 1催化活性的混合抑制剂，对PARP - 1的催化活性和底物结合亲和力均有影响。通过RNA干扰使PARP - 1缺失导致失活X染色体上的报告基因重新激活，表明PARP - 1参与维持基因沉默。这些结果表明，macroH2A在基因沉默中的一个功能是抑制PARP - 1的酶活性，这可能会影响PARP - 1与染色质的结合。
