tailieunhanh - Báo cáo khoa học: Requirements for chromatin reassembly during transcriptional downregulation of a heat shock gene in Saccharomyces cerevisiae

Heat shock genes respond to moderate heat stress by a wave of transcrip-tion. 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) tran-scription unit. | ễFEBS Journal Requirements for chromatin reassembly during transcriptional downregulation of a heat shock gene in Saccharomyces cerevisiae Mette M. Jensen Marianne S. Christensen Bjarne Bonven and Torben H. Jensen Centre for mRNP Biogenesis and Metabolism Department of Molecular Biology University of Aarhus Denmark Keywords histone chaperones histone reassembly HSP104 SPT16 SPT6 Correspondence B. Bonven Department of Molecular Biology University of Aarhus . Mollers Alle Building 130 DK 8000 Aarhus C Denmark Fax 45 8619 6500 Tel 45 8942 2678 E-mail bjb@ Received 8 January 2008 revised 2 April 2008 accepted 4 April 2008 doi 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 H3D4-30 is normally deposited reassembly of H3A440 is obliterated with an accompanying sustained transcription. On mutation of the histone chaperones Spt6p and Spt16p but not Asflp 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. The impediment to transcriptional activity posed by eukaryotic chromatin structure has been recognized for four decades 1 . Intense studies in recent years have shed light on the cellular mechanisms allowing transcription to occur on nucleosomal templates. These mechanisms involve a plethora of covalent histone modifications a complex set of chromatin remodelling activities and .