Pato M L, Karlok M, Wall C, Higgins N P
Department of Microbiology, University of Colorado Health Sciences Center, Denver 80262, USA.
J Bacteriol. 1995 Oct;177(20):5937-42. doi: 10.1128/jb.177.20.5937-5942.1995.
Bacteriophage Mu contains an unusually strong DNA gyrase binding site (SGS), located near the center of its genome, that is required for efficient Mu DNA replication (M. L. Pato, Proc. Natl. Acad. Sci. USA 91:7056-7060, 1994; M. L. Pato, M. M. Howe, and N. P. Higgins, Proc. Natl. Acad. Sci. USA 87:8716-8720, 1990). Replication of wild-type Mu initiates about 10 min after induction of a lysogen, while replication in the absence of the SGS is delayed about an hour. To determine which step in the replication pathway is blocked in the absence of the SGS, we inactivated the SGS by deletion and by insertion and studied the effects of these alterations on various stages of Mu DNA replication. Following induction in the absence of a functional SGS, early transcription and synthesis of the Mu-encoded replication proteins occurred normally. However, neither strand transfer nor cleavage at the Mu genome termini could be detected 40 min after induction. The data are most consistent with a requirement for the SGS in the efficient synapsis of the Mu prophage termini to form a separate chromosomal domain.
噬菌体Mu含有一个异常强大的DNA回旋酶结合位点（SGS），位于其基因组中心附近，这是高效进行Mu DNA复制所必需的（M. L. 帕托，《美国国家科学院院刊》91:7056 - 7060，1994；M. L. 帕托、M. M. 豪和N. P. 希金斯，《美国国家科学院院刊》87:8716 - 8720，1990）。野生型Mu的复制在溶原菌诱导后约10分钟开始，而在没有SGS的情况下复制会延迟约一小时。为了确定在没有SGS时复制途径中的哪个步骤被阻断，我们通过缺失和插入使SGS失活，并研究了这些改变对Mu DNA复制各个阶段的影响。在没有功能性SGS的情况下诱导后，Mu编码的复制蛋白的早期转录和合成正常发生。然而，诱导40分钟后，在Mu基因组末端既未检测到链转移也未检测到切割。这些数据最符合在Mu原噬菌体末端有效联会以形成一个单独染色体结构域时对SGS的需求。
