Jensen Mette M, Christensen Marianne S, Bonven Bjarne, Jensen Torben H
Centre for mRNP Biogenesis and Metabolism, Department of Molecular Biology, University of Aarhus, Denmark.
FEBS J. 2008 Jun;275(11):2956-64. doi: 10.1111/j.1742-4658.2008.06451.x. Epub 2008 Apr 25.
Heat shock genes respond to moderate heat stress by a wave of transcription. The induction phase is accompanied by the massive eviction of histones, which later reassemble with DNA during the ensuing phase of transcription downregulation. In this article, we identify determinants of this reassembly throughout the heat shock protein 104 gene (HSP104) transcription unit. The results show that, although histone H3 lacking amino acids 4-30 of its N-terminal tail (H3Delta4-30) is normally deposited, reassembly of H3Delta4-40 is obliterated with an accompanying sustained transcription. On mutation of the histone chaperones Spt6p and Spt16p, but not Asf1p, reassociation of H3 with DNA is compromised. However, despite a lasting open chromatin structure, transcription ceases normally in the spt6 mutant. Thus, transcriptional downregulation can be uncoupled from histone redeposition and ongoing transcription is not required to prevent chromatin reassembly.
热休克基因通过一波转录对适度热应激做出反应。诱导阶段伴随着组蛋白的大量移除，随后在转录下调的后续阶段，组蛋白与DNA重新组装。在本文中，我们确定了整个热休克蛋白104基因（HSP104）转录单元中这种重新组装的决定因素。结果表明，虽然缺乏N端尾巴氨基酸4 - 30的组蛋白H3（H3Delta4 - 30）通常会沉积，但H3Delta4 - 40的重新组装被消除，并伴随着持续转录。在组蛋白伴侣Spt6p和Spt16p发生突变时，但Asf1p未发生突变时，H3与DNA的重新结合受到损害。然而，尽管染色质结构持续开放，但在spt6突变体中转录正常停止。因此，转录下调可以与组蛋白重新沉积解偶联，并且不需要持续转录来防止染色质重新组装。
