Alekseyenko Artyom A, Gorchakov Andrey A, Zee Barry M, Fuchs Stephen M, Kharchenko Peter V, Kuroda Mitzi I
Division of Genetics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA;
Division of Genetics, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA; Institute of Molecular and Cellular Biology, Novosibirsk 630090, Russia;
Genes Dev. 2014 Jul 1;28(13):1445-60. doi: 10.1101/gad.241950.114.
Heterochromatin protein 1 (HP1a) has conserved roles in gene silencing and heterochromatin and is also implicated in transcription, DNA replication, and repair. Here we identify chromatin-associated protein and RNA interactions of HP1a by BioTAP-XL mass spectrometry and sequencing from Drosophila S2 cells, embryos, larvae, and adults. Our results reveal an extensive list of known and novel HP1a-interacting proteins, of which we selected three for validation. A strong novel interactor, dADD1 (Drosophila ADD1) (CG8290), is highly enriched in heterochromatin, harbors an ADD domain similar to human ATRX, displays selective binding to H3K9me2 and H3K9me3, and is a classic genetic suppressor of position-effect variegation. Unexpectedly, a second hit, HIPP1 (HP1 and insulator partner protein-1) (CG3680), is strongly connected to CP190-related complexes localized at putative insulator sequences throughout the genome in addition to its colocalization with HP1a in heterochromatin. A third interactor, the histone methyltransferase MES-4, is also enriched in heterochromatin. In addition to these protein-protein interactions, we found that HP1a selectively associated with a broad set of RNAs transcribed from repetitive regions. We propose that this rich network of previously undiscovered interactions will define how HP1a complexes perform their diverse functions in cells and developing organisms.
异染色质蛋白1（HP1a）在基因沉默和异染色质中具有保守作用，并且还与转录、DNA复制及修复有关。在此，我们通过BioTAP-XL质谱分析以及对果蝇S2细胞、胚胎、幼虫和成虫的测序，鉴定了与HP1a相关的染色质蛋白和RNA相互作用。我们的结果揭示了大量已知和新发现的与HP1a相互作用的蛋白质，我们从中挑选了三种进行验证。一种强大的新相互作用蛋白dADD1（果蝇ADD1）（CG8290）在异染色质中高度富集，含有一个与人类ATRX相似的ADD结构域，对H3K9me2和H3K9me3具有选择性结合，并且是位置效应斑驳的经典遗传抑制因子。出乎意料的是，第二个发现的相互作用蛋白HIPP1（HP1和绝缘子伴侣蛋白-1）（CG3680），除了在异染色质中与HP1a共定位外，还与位于全基因组假定绝缘子序列处的CP190相关复合物紧密相连。第三个相互作用蛋白，组蛋白甲基转移酶MES-4，也在异染色质中富集。除了这些蛋白质-蛋白质相互作用外，我们还发现HP1a与从重复区域转录的大量RNA选择性相关。我们提出，这个以前未被发现的丰富相互作用网络将定义HP1a复合物如何在细胞和发育中的生物体中发挥其多样的功能。
