Kuldell N, Hochschild A
Department of Microbiology and Molecular Genetics, Harvard Medical School, Boston, Massachusetts 02115.
J Bacteriol. 1994 May;176(10):2991-8. doi: 10.1128/jb.176.10.2991-2998.1994.
The phage lambda repressor activates transcription of its own gene from the promoter PRM. Previous work has suggested that this activation involves a protein-protein interaction between DNA-bound repressor and RNA polymerase. To identify the subunit of RNA polymerase that participates in this putative interaction, we searched for polymerase mutants that responded poorly to repressor. We report here the isolation of three sigma mutants that caused defects in repressor-stimulated, but not basal, transcription from PRM. These mutants bear amino acid substitutions in a putative helix-turn-helix motif that sigma uses to recognize the promoter -35 region. We suggest that lambda repressor interacts directly with this helix-turn-helix motif in facilitating the formation of a productive initiating complex.
λ噬菌体阻遏物从启动子PRM激活其自身基因的转录。先前的研究表明，这种激活涉及DNA结合的阻遏物与RNA聚合酶之间的蛋白质-蛋白质相互作用。为了鉴定参与这种假定相互作用的RNA聚合酶亚基，我们寻找了对阻遏物反应不佳的聚合酶突变体。我们在此报告分离出三个σ突变体，它们在PRM的阻遏物刺激的而非基础的转录中导致缺陷。这些突变体在σ用于识别启动子-35区域的假定螺旋-转角-螺旋基序中存在氨基酸替换。我们认为，λ阻遏物在促进形成有活性的起始复合物过程中直接与该螺旋-转角-螺旋基序相互作用。
