Iida S, Meyer J, Kennedy K E, Arber W
EMBO J. 1982;1(11):1445-53. doi: 10.1002/j.1460-2075.1982.tb01336.x.
The bacteriophage P1 genome carries an invertible C segment consisting of 3-kb unique sequences flanked by 0.6-kb inverted repeats. With insertion and deletion mutants of P1 derivatives the site-specific recombinase gene cin for C inversion) has been mapped adjacent to the C segment and the cix sites (for C inversion cross-over) have been located at the outside ends of the inverted repeats. Inversion of the C segment functions as a biological switch and controls expression of the gene(s) responsible for phage infectivity carried on the C segment. The cin gene product can promote recombination between a 'quasi- cix ' site on plasmid pBR322 and a cix site on P1 DNA. The junctions formed on the resulting co-integrate can also serve as cix sites. This observation implies a potential evolutionary process to bring genes under the control of a biological switch acting by DNA inversion.
噬菌体P1基因组携带一个可反转的C片段，该片段由3kb的独特序列组成，两侧为0.6kb的反向重复序列。利用P1衍生物的插入和缺失突变体，已将负责C片段反转的位点特异性重组酶基因cin定位在C片段附近，而cix位点（用于C片段反转交叉）则位于反向重复序列的外侧末端。C片段的反转起到生物开关的作用，控制着C片段上负责噬菌体感染性的基因的表达。cin基因产物可促进质粒pBR322上的“准cix”位点与P1 DNA上的cix位点之间的重组。在产生的共整合体上形成的连接点也可作为cix位点。这一观察结果暗示了一个潜在的进化过程，使基因受通过DNA反转起作用的生物开关的控制。
