9 Геном, плазмиды, вирусы (1160078), страница 9
Текст из файла (страница 9)
The CI and Cro proteinsare repressors, and the CII protein is an activator. The N and Q proteins interact directly with the E. coli RNA polymerase to permit readthrough (i.e., transcription) of certain transcription termination sequences built into the phage DNA genome. This activity of the N and Qproteins is referred to as antitermination, and it is distinct from theregulatory mechanisms described to this point.Lysis In the lytic pathway (Fig.
27-26), phage genes are arranged inthree sets according to their time of expression. Some products of genesexpressed in the first stage (immediate-early) are required to permittranscription of second-stage genes (delayed-early). The products ofsome second-stage genes, in turn, are required to permit transcriptionin the last stage (late genes). In general, genes required for replicationand recombination are expressed early, and genes required for assembling phage peptides and lysing the host cell are expressed late. The Nand Q proteins are the key to temporal regulation of the expression ofbacteriophage genes.965.
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