Balance between Distinct HP1 Family Proteins Controls Heterochromatin Assembly in Fission Yeast
Balance between Distinct HP1 Family Proteins Controls Heterochromatin Assembly in Fission Yeast
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DOI：
10.1128/mcb.00791-08
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发表时间：
2008-12-01
影响因子：
5.3
通讯作者：
Nakayama, Jun-ichi
中科院分区：
文献类型：
--
作者：
Sadaie, Mahito;Kawaguchi, Rika;Nakayama, Jun-ichi
异染色质蛋白1（Heterochromatin protein 1，HP1）是一种在染色体上高度保守的蛋白质，在染色质包装和基因沉默中具有重要作用。在裂殖酵母中，两个HP1家族蛋白Swi6和Chp2参与异染色质区域的转录沉默，但它们如何发挥作用以及它们在异染色质组装中是否协同或差异发挥作用仍然难以捉摸。在这里，我们表明，Swi6和Chp2的组装所需的完全抑制异染色质，其中他们发挥独特的，不重叠的作用。Swi6表达丰富，并通过其自缔合特性在形成抑制结构中发挥剂量依赖性作用。相比之下，Chp2以较低水平表达，不显示简单的剂量依赖性抑制活性。然而，它有助于招募染色质调节因子Clr 3和Epe 1，并具有结合与其沉默功能密切相关的富含染色质的核亚组分的新能力。最后，我们证明了Swi6和Chp2之间的适当平衡对于异染色质组装至关重要。我们的研究结果提供了新的见解不同的和合作的功能，多个HP1家族蛋白在形成高阶染色质结构。
Heterochromatin protein 1 ( HP1) is a conserved chromosomal protein with important roles in chromatin packaging and gene silencing. In fission yeast, two HP1 family proteins, Swi6 and Chp2, are involved in transcriptional silencing at heterochromatic regions, but how they function and whether they act cooperatively or differentially in heterochromatin assembly remain elusive. Here, we show that both Swi6 and Chp2 are required for the assembly of fully repressive heterochromatin, in which they play distinct, nonoverlapping roles. Swi6 is expressed abundantly and plays a dose-dependent role in forming a repressive structure through its self-association property. In contrast, Chp2, expressed at a lower level, does not show a simple dose-dependent repressive activity. However, it contributes to the recruitment of chromatin-modulating factors Clr3 and Epe1 and possesses a novel ability to bind the chromatin-enriched nuclear subfraction that is closely linked with its silencing function. Finally, we demonstrate that a proper balance between Swi6 and Chp2 is critical for heterochromatin assembly. Our findings provide novel insight into the distinct and cooperative functions of multiple HP1 family proteins in the formation of higher-order chromatin structure.