Phage T4 SegB protein is a homing endonuclease required for the preferred inheritance of T4 tRNA gene region occurring in co-infection with a related phage
Phage T4 SegB protein is a homing endonuclease required for the preferred inheritance of T4 tRNA gene region occurring in co-infection with a related phage
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DOI：
10.1093/nar/gkn053
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发表时间：
2008-04-01
影响因子：
14.9
通讯作者：
Granovsky, Igor E.
中科院分区：
文献类型：
--
作者：
Brok-Volchanskaya, Vera S.;Kadyrov, Farid A.;Granovsky, Igor E.
归巢内切酶通过裂解受体DNA来启动包含其自身基因和侧翼序列的DNA片段的非互惠转移。噬菌体T4片段B基因位于一组tRNA基因中，编码一种功能未知的蛋白质，与GIY-YIG家族的同源内切酶同源。我们证明了SegB蛋白是一种位点特异性内切酶，在其DNA裂解位点上主要产生3个2-nT突起末端。对SegB裂解位点的分析表明，SegB识别27个碱基的序列。它含有11个碱基的保守序列，对应于tRNA TC茎环的保守基序，而其余的识别位点是相当简并的。与T4相关的噬菌体T2L、RB1和RB3含有与T4同源的tRNA基因区，但缺少SegB基因和几个tRNA基因。在T4噬菌体和T2L噬菌体的混合感染中，SegB基因的遗传效率接近100%。首选遗传完全依赖于SegB基因的完整性，并伴随着T2L tRNA基因区域标记的丢失。我们认为SegB是一种归巢内切酶，它的功能是确保自己的基因和周围的tRNA基因在T4相关噬菌体中传播。
Homing endonucleases initiate nonreciprocal transfer of DNA segments containing their own genes and the flanking sequences by cleaving the recipient DNA. Bacteriophage T4 segB gene, which is located in a cluster of tRNA genes, encodes a protein of unknown function, homologous to homing endonucleases of the GIY-YIG family. We demonstrate that SegB protein is a site-specific endonuclease, which produces mostly 3 2-nt protruding ends at its DNA cleavage site. Analysis of SegB cleavage sites suggests that SegB recognizes a 27-bp sequence. It contains 11-bp conserved sequence, which corresponds to a conserved motif of tRNA TC stem-loop, whereas the remainder of the recognition site is rather degenerate. T4-related phages T2L, RB1 and RB3 contain tRNA gene regions that are homologous to that of phage T4 but lack segB gene and several tRNA genes. In co-infections of phages T4 and T2L, segB gene is inherited with nearly 100 of efficiency. The preferred inheritance depends absolutely on the segB gene integrity and is accompanied by the loss of the T2L tRNA gene region markers. We suggest that SegB is a homing endonuclease that functions to ensure spreading of its own gene and the surrounding tRNA genes among T4-related phages.