Regulation of Lysogeny by Phage P1 and P7

噬菌体P1和P7的IMMC和IMMI区域密切相关，但具有异种免疫性，它们编码的调节蛋白参与了噬菌体的裂解或溶原性生长。在IMMC中，C_1编码裂解基因表达的抑制因子，而COI编码C_1抑制活性的拮抗剂。在IMMI中编码的C4抑制物可以阻止Ant的表达，Ant是一种紧密相连的基因，其产物干扰了c1介导的抑制。P1和P7在C4特异性上的差异是造成其异种免疫特性的原因。IMMC和IMMI内基因表达的调控将通过监测在编码噬菌体调节蛋白的兼容质粒存在的情况下从转录融合中获得的LacZ的表达来进行。通过体外诱变和DNA酶保护研究，将研究IMMC内多个C1操纵子位点所起的调节作用。还将寻找抑制CoI过度生产所导致的毒力表型的C1突变。P1ImmI和P7IMMI序列差异对异种免疫特异性的贡献将通过分析c4和ANT表达对这些区域以及含有裂解复制子的下游区域转录的影响来研究。

The ImmC and ImmI regions of the closely related, but heteroimmune, phages P1 and P7 code for regulatory proteins involved in directing the phage toward lytic or lysogenic growth. Within ImmC, c1 codes for a repressor of lytic gene expression, while coi codes for an antagonist of c1 repressor activity. The c4 repressor, encoded within ImmI, prevents expression of ant, a closely linked gene whose product interferes with c1-mediated repression. Differences in c4 specificity are responsible for the heteroimmune character of P1 and P7. Regulation of gene expression within ImmC and ImmI will be investigated by monitoring the expression of lacZ from transcriptional fusions in the presence of compatible plasmids coding for phage regulatory proteins. The regulatory role played by multiple c1 operator sites within ImmC will be investigated by in vitro mutagenesis and DNase protection studies. Mutations in c1 that suppress the virulent phenotype caused by Coi overproduction will also be sought. The contribution to heteroimmune specificity of sequence differences within P1ImmI and P7 ImmI will be investigated by assaying the effect of c4 and ant expression on transcription within these regions, and within the downstream region containing the lytic replicon.//