Wu C H, Lin H, Black L W
Department of Biological Chemistry, University of Maryland School of Medicine, Baltimore 21201, USA.
J Mol Biol. 1995 Apr 7;247(4):523-8.
Bacteriophage T4 genes 16 and 19 containing the 24 bp homology regions that recombine to form Hp17 mutants were cloned into plasmids. When the two homology sequences were cloned either together into one or separately into two compatible plasmids, a polymerase chain reaction assay showed that recombination occurred in vivo. The recombinant sequence was identical with that found in T4 phage Hp17 mutants, and was produced in recombination-deficient Escherichia coli. Mutational analysis revealed a requirement for functional gene 16 but not gene 17 to recombine the sequences. Moreover, gp16, the terminase small subunit, was required, since an amber gene 16 produced the recombinant sequence only when suppressed. Mutations in the gene 16 recombination sequence (3GA and 15TG) that eliminated Hp17 formation in T4 phage increased the synthesis of the large terminase subunit, gp17 in T4 infections, suggesting gp16 interaction with this site. gp16 binding to gene 16 and gene 19 pac-like sites may synapse the homologous sequences to lead to Hp17 mutant formation, and this suggests a synapsis mechanism for control of T4 DNA maturation and concatemer processing in packaging.
含有24bp同源区域并重组形成Hp17突变体的噬菌体T4基因16和19被克隆到质粒中。当两个同源序列一起克隆到一个质粒中或分别克隆到两个相容的质粒中时，聚合酶链反应分析表明体内发生了重组。重组序列与在T4噬菌体Hp17突变体中发现的序列相同，并且在重组缺陷型大肠杆菌中产生。突变分析表明，重组这些序列需要功能性基因16而不是基因17。此外，由于琥珀型基因16仅在被抑制时才产生重组序列，因此需要末端酶小亚基gp16。T4噬菌体中消除Hp17形成的基因16重组序列（3GA和15TG）中的突变增加了T4感染时大末端酶亚基gp17的合成，这表明gp16与该位点相互作用。gp16与基因16和基因19的pac样位点结合可能使同源序列发生联会，从而导致Hp17突变体形成，这提示了一种在包装过程中控制T4 DNA成熟和多联体加工的联会机制。
