Heat shock genes respond to moderate heat stress by a wave of transcription. The induction phase is accompanied by massive eviction of histones, which later reassemble with DNA during the ensuing phase of transcription downregulation. Here, we identify determinants of this reassembly throughout the HSP104 transcription unit. The results show that while histone H3 lacking amino acids 4 through 30 of its N-terminal tail (H3Δ4-30) is normally deposited, reassembly of H3Δ4-40 is obliterated with an accompanying sustained transcription. Upon mutation of 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 redepositioning and ongoing transcription is not required to prevent chromatin reassembly.
F E B S Journal, 2008, Vol 275, Issue 11, p. 2956-2964