Flanigan Asa, Gardner Jeffrey F
Department of Microbiology, University of Illinois at Urbana-Champaign, 601 South Goodwin Avenue, Urbana, IL 61801, USA.
J Bacteriol. 2007 Sep;189(17):6303-11. doi: 10.1128/JB.00577-07. Epub 2007 Jun 29.
The Gifsy-1 phage integrates site specifically into the Salmonella chromosome via an integrase-mediated site-specific recombination mechanism. Initial genetic analysis suggests that Gifsy-1 integrase-mediated excision of the Gifsy-1 phage is influenced by proteins encoded by both the Gifsy-1 and the Gifsy-2 phages. Our studies show that the Gifsy-1 Xis protein regulates the directionality of integrase-mediated excision of the Gifsy-1 phage. Electrophoretic mobility shift assays, DNase I footprinting, dimethyl sulfate (DMS) interference assays, and DMS protection assays were used to identify a 31-base-pair sequence in the attP region to which the Gifsy-1 protein binds. The results suggest that this recombination directionality factor binds in vitro to three imperfect direct repeats, spaced 10 base pairs apart, in a sequential and cooperative manner in the absence of other phage-encoded proteins. Our studies suggest that, while the Gifsy-1 Xis does not require additional factors for specific and high-affinity binding, it may form a microfilament on DNA similar to that described for the phage lambda Xis protein.
Gifsy-1噬菌体通过整合酶介导的位点特异性重组机制特异性地整合到沙门氏菌染色体中。初步遗传分析表明，Gifsy-1整合酶介导的Gifsy-1噬菌体切除受Gifsy-1和Gifsy-2噬菌体编码的蛋白质影响。我们的研究表明，Gifsy-1 Xis蛋白调节Gifsy-1噬菌体整合酶介导的切除方向。采用电泳迁移率变动分析、DNase I足迹分析、硫酸二甲酯（DMS）干扰分析和DMS保护分析来鉴定attP区域中Gifsy-1蛋白结合的一个31个碱基对的序列。结果表明，在没有其他噬菌体编码蛋白的情况下，这种重组方向性因子在体外以连续且协同的方式与三个间隔10个碱基对的不完全直接重复序列结合。我们的研究表明，虽然Gifsy-1 Xis不需要额外的因子进行特异性和高亲和力结合，但它可能在DNA上形成类似于噬菌体λ Xis蛋白所描述的微丝。
