Kataoka Kensuke, Noto Tomoko, Mochizuki Kazufumi
Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), A-1030 Vienna, Austria
Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA), A-1030 Vienna, Austria.
Proc Natl Acad Sci U S A. 2016 Aug 9;113(32):9027-32. doi: 10.1073/pnas.1606012113. Epub 2016 Jul 27.
Multiple heterochromatic loci are often clustered into a higher order nuclear architecture called a heterochromatin body in diverse eukaryotes. Although phosphorylation of Heterochromatin Protein 1 (HP1) family proteins regulates heterochromatin dynamics, its role in heterochromatin bodies remains unknown. We previously reported that dephosphorylation of the HP1-like protein Pdd1p is required for the formation of heterochromatin bodies during the process of programmed DNA elimination in the ciliated protozoan Tetrahymena Here, we show that the heterochromatin body component Jub4p is required for Pdd1p phosphorylation, heterochromatin body formation, and DNA elimination. Moreover, our analyses of unphosphorylatable Pdd1p mutants demonstrate that Pdd1p phosphorylation is required for heterochromatin body formation and DNA elimination, whereas it is dispensable for local heterochromatin assembly. Therefore, both phosphorylation and the following dephosphorylation of Pdd1p are necessary to facilitate the formation of heterochromatin bodies. We suggest that Jub4p-mediated phosphorylation of Pdd1p creates a chromatin environment that is a prerequisite for subsequent heterochromatin body assembly and DNA elimination.
在多种真核生物中，多个异染色质位点常常聚集形成一种称为异染色质体的高阶核结构。尽管异染色质蛋白1（HP1）家族蛋白的磷酸化调节异染色质动态变化，但其在异染色质体中的作用仍不清楚。我们之前报道过，在纤毛原生动物四膜虫程序性DNA消除过程中，类HP1蛋白Pdd1p的去磷酸化是异染色质体形成所必需的。在此，我们表明异染色质体成分Jub4p是Pdd1p磷酸化、异染色质体形成和DNA消除所必需的。此外，我们对不可磷酸化的Pdd1p突变体的分析表明，Pdd1p磷酸化是异染色质体形成和DNA消除所必需的，而对于局部异染色质组装则是可有可无的。因此，Pdd1p的磷酸化及其后的去磷酸化对于促进异染色质体的形成都是必要的。我们认为，Jub4p介导的Pdd1p磷酸化创造了一种染色质环境，这是随后异染色质体组装和DNA消除的先决条件。
