Thompson R, Taylor L, Kelly K, Everett R, Willetts N
EMBO J. 1984 May;3(5):1175-80. doi: 10.1002/j.1460-2075.1984.tb01947.x.
The DNA sequence of the F plasmid origin of conjugal DNA transfer, oriT , has been determined. The origin lies in an intercistronic region which contains several inverted repeat sequences and a long AT-rich tract. Introduction of a nick into one of the DNA strands in the oriT region precedes the initiation of conjugal DNA replication, and the position of the strand-specific nicks acquired by a lambda oriT genome upon propagation in Flac-carrying cells has been determined. The nicks were not uniquely positioned, rather there was a cluster of three major and up to 20 minor sites: the biological significance of this observation is not yet fully clear. Nine independent point mutations which inactivate oriT function have been sequenced and found to alter one or other of two nucleotide positions which lie 14 and 19 bp to one side of the rightmost (as drawn) major nick site. These key nucleotides may lie in a recognition sequence for the oriT endonuclease, since mutations at these sites prevent nicking at oriT .
F质粒接合性DNA转移起点oriT的DNA序列已被确定。该起点位于一个基因间区域，其中包含几个反向重复序列和一个富含AT的长片段。在接合性DNA复制起始之前，oriT区域的一条DNA链会引入一个切口，并且已经确定了λoriT基因组在携带Flac的细胞中繁殖时获得的链特异性切口的位置。切口并非定位在唯一位置，而是有一个由三个主要位点和多达20个次要位点组成的簇：这一观察结果的生物学意义尚未完全明确。已对9个使oriT功能失活的独立点突变进行了测序，发现它们改变了位于最右侧（如图所示）主要切口位点一侧14和19个碱基对处的两个核苷酸位置中的一个或另一个。这些关键核苷酸可能位于oriT内切核酸酶的识别序列中，因为这些位点的突变会阻止oriT处的切口形成。
