Hickey Anthony J, Conway de Macario Everly, Macario Alberto J L
Wadsworth Center, Division of Molecular Medicine, New York State Department of Health, Albany 12201-0509, USA.
Crit Rev Biochem Mol Biol. 2002;37(4):199-258. doi: 10.1080/10409230290771500.
A brief survey is presented of salient findings on transcription in the Archaea, focussing on stress genes of the hsp70(dnaK) locus, which code for the molecular chaperones Hsp70(DnaK), Hsp40(DnaJ), and GrpE. Archaeal basal factors and some recently characterized regulators pertinent to non-stress genes are presented first to show their similarities and differences with equivalents in organisms of the other two phylogenetic domains, Bacteria and Eucarya, and to reveal clues on how these or similar factors might transcribe and regulate the archaeal stress genes. The second part of the article deals with the hsp70(dnaK)-locus genes, particularly those from Methanosarcina mazeii, because they are virtually the only ones within the methanogenic Archaea whose patterns of constitutive and stress-induced expressions have been studied. Therefore, these genes, provide a standardized model system to elucidate transcription initiation and regulation at the molecular level in this phylogenetic group. Promoters, and other cis-acting sites that are, or might be, involved in stress-gene expression are described. Conformational changes of basal transcription factors after interaction with stress-gene promoters are discussed that suggest ways for generating a large diversity of initiation complexes using a few factors and DNA sites in different combinations. Likewise, the effects of stress on DNA topology and on TBP-TFB-promoter complex formation and tightness are described, which might also contribute to the generation of transcription-initiation complex diversity. This diversity would be key to differential gene expression, namely, which genes are transcribed, when (basal, steady expression vs. sporadic stress-induced expression), and to what level. Future research should investigate this diversity, and the mechanism of complex formation and action at the atomic, molecular, and supramolecular levels to elucidate the dynamics of transcription initiation in real time.
本文简要综述了古菌转录方面的显著发现，重点关注hsp70(dnaK)位点的应激基因，这些基因编码分子伴侣Hsp70(DnaK)、Hsp40(DnaJ)和GrpE。首先介绍古菌基础因子和一些最近鉴定的与非应激基因相关的调控因子，以展示它们与其他两个系统发育域（细菌和真核生物）中对应因子的异同，并揭示这些或类似因子如何转录和调控古菌应激基因的线索。文章的第二部分讨论hsp70(dnaK)位点的基因，特别是来自马氏甲烷八叠球菌的那些基因，因为它们几乎是产甲烷古菌中唯一其组成型和应激诱导表达模式已被研究的基因。因此，这些基因提供了一个标准化的模型系统，以在分子水平阐明该系统发育组中的转录起始和调控。描述了与应激基因表达相关或可能相关的启动子和其他顺式作用位点。讨论了基础转录因子与应激基因启动子相互作用后的构象变化，这些变化提示了利用少数因子和DNA位点以不同组合产生大量起始复合物的方式。同样，描述了应激对DNA拓扑结构以及对TBP-TFB-启动子复合物形成和紧密性的影响，这也可能有助于产生转录起始复合物的多样性。这种多样性对于差异基因表达至关重要，即哪些基因被转录、何时转录（基础、稳定表达与偶发应激诱导表达）以及转录到何种水平。未来的研究应在原子、分子和超分子水平研究这种多样性以及复合物形成和作用的机制，以实时阐明转录起始的动力学。
