Dialynas George K, Terjung Stefan, Brown Jeremy P, Aucott Rebecca L, Baron-Luhr Bettina, Singh Prim B, Georgatos Spyros D
The Stem Cell and Chromatin Group, Laboratory of Biology, The University of Ioannina, School of Medicine and The Institute of Biomedical Research (FORTH/BRI), 45 110 Ioannina, Greece.
J Cell Sci. 2007 Oct 1;120(Pt 19):3415-24. doi: 10.1242/jcs.012914. Epub 2007 Sep 12.
We have compared the distribution of endogenous heterochromatin protein 1 (HP1) proteins (alpha, beta and gamma) in different epithelial lines, pluripotent stem cells and embryonic fibroblasts. In parallel, we have interrogated assembly and dynamics of newly expressed HP1-GFP proteins in cells lacking both HP1alpha and HP1beta alleles, blocked at the G1-S boundary, or cultured in the presence of HDAC and HAT inhibitors. The results reveal a range of cell type and differentiation state-specific patterns that do not correlate with 'fast' or 'slow' subunit exchange in heterochromatin. Furthermore, our observations show that targeting of HP1gamma to heterochromatic sites depends on HP1alpha and H1beta and that, on an architectural level, HP1alpha is the most polymorphic variant of the HP1 family. These data provide evidence for HP1 plasticity under shifting microenvironmental conditions and offer a new conceptual framework for understanding chromatin dynamics at the molecular level.
我们比较了内源性异染色质蛋白1（HP1）的三种蛋白（α、β和γ）在不同上皮细胞系、多能干细胞和胚胎成纤维细胞中的分布情况。同时，我们研究了在缺乏HP1α和HP1β等位基因、停滞在G1-S边界或在HDAC和HAT抑制剂存在的条件下培养的细胞中，新表达的HP1-GFP蛋白的组装和动力学。结果揭示了一系列细胞类型和分化状态特异性模式，这些模式与异染色质中“快速”或“缓慢”的亚基交换无关。此外，我们的观察结果表明，HP1γ靶向异染色质位点依赖于HP1α和H1β，并且在结构水平上，HP1α是HP1家族中最具多态性的变体。这些数据为HP1在不断变化的微环境条件下的可塑性提供了证据，并为在分子水平上理解染色质动力学提供了一个新的概念框架。
