ROLE OF GENE-V PROTEIN IN F1-SINGLE-STRAND SYNTHESIS
ROLE OF GENE-V PROTEIN IN F1-SINGLE-STRAND SYNTHESIS
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DOI：
10.1016/0042-6822(75)90289-5
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发表时间：
1975-01-01
期刊：
影响因子：
3.7
通讯作者：
ZINDER, ND
中科院分区：
文献类型：
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作者：
MAZUR, BJ;ZINDER, ND
我们证明，在感染噬菌体F1的细胞中，只有基因V蛋白，DNA结合蛋白，是必要的影响开关从双链合成到单链合成，我们特别表明，除了那些已经需要的双链合成没有主机蛋白需要单链合成。通过在限制性温度下孵育，使f1温度敏感性（ts）基因II感染的细胞在不存在DNA复制的情况下积累过量的基因V蛋白。然后在氯霉素存在下将感染的细胞转移到允许的温度;随后进行单链合成。然而，当用野生型f1感染的细胞进行相同的实验时，合成的是双链而不是单链。由于这两个实验之间的主要区别在于thetsII感染中过量的基因V蛋白的积累，因此在野生型感染中单链合成必须停止，因为没有游离的基因V蛋白可用，而不是因为氯霉素敏感的宿主蛋白被耗尽。氯霉素通过阻止蛋白质合成，显然阻断了通常用于单链合成的基因V蛋白的两个来源。不能合成新的基因V蛋白，并且所有先前合成的基因V蛋白保持与先前存在的单链稳定复合，而不是在单链的形态发生期间被回收。在没有新的和回收的基因V蛋白，双链合成results.If未能回收基因V蛋白确实是氯霉素治疗引起的病变，然后灭活特定的f1基因产物所需的形态，通过使用琥珀和温度敏感的突变体噬菌体，也可能导致单链合成的双链合成的替代。这样的单链合成的停止确实被发现感染后的突变体在基因I，IV，VII和VIII，但不是感染后的突变体在基因III和VI。因此，基因III和VI蛋白在形态发生中的作用比基因I、IV、VII和VIII蛋白晚;它们似乎在单链和基因V蛋白分离后起作用。从温度变化实验中获得的数据表明，在受感染的细胞中，基因V蛋白的供应受到仔细的调节，并且从来没有多少游离的基因V蛋白可用。
We demonstrate that, in cells infected with phage f1, only the gene V protein, a DNA-binding protein, is necessary to effect the switch from double- to single-strand synthesis; we specifically show that no host proteins are required for single-strand synthesis beyond those that are already required for double-strand synthesis. f1 temperature-sensitive (ts) gene II-infected cells were allowed to accumulate excess gene V protein in the absence of DNA replication through incubation at restrictive temperature. The infected cells were then shifted to permissive temperature in the presence of chloramphenicol; single-strand synthesis ensued. When, however, the identical experiment was performed with wild-type f1-infected cells, double, rather than single strands were synthesized. Since the principal difference between the two experiments lay in the accumulation of excess gene V protein in thetsII infection, single-strand synthesis must have halted in the wild-type infection because no free gene V protein was available and not because a chloramphenicol-sensitive host protein was being depleted. Chloramphenicol, by preventing protein synthesis, apparently blocks the two sources of gene V protein normally used for single-strand synthesis. No new gene V protein can be synthesized, and all previously synthesized gene V protein remains stably complexed with preexisting single strands rather than being recycled during morphogenesis of the single strands. In the absence of both new and recycled gene V protein, double-strand synthesis resumes.If a failure to recycle gene V protein were indeed the lesion induced by chloramphenicol treatment, then inactivation of specific f1 gene products required for morphogenesis, through use of amber and temperature-sensitive mutant phage, might also lead to replacement of single-strand synthesis by double-strand synthesis. Such cessation of single-strand synthesis was indeed found after infections by mutants in genes I, IV, VII, and VIII but not after infections by mutants in genes III and VI. The gene III and VI proteins therefore act at a later step in morphogenesis than the gene I, IV, VII, and VIII proteins; they appear to function after the single strands and gene V protein have separated. Data obtained from temperature shift experiments indicate that the supply of gene V protein in an infected cell is carefully regulated and that there is never much free gene V protein available.