Bertani L E
Proc Natl Acad Sci U S A. 1970 Feb;65(2):331-6. doi: 10.1073/pnas.65.2.331.
Both prophage integration in bacteriophage P2 and the reverse event, prophage excision, are known to require a specific phage gene product, the so-called int function. We find that P2 can integrate efficiently at a free attachment site also in an immune host (i.e., in the presence of phage specific repressor) provided the superinfecting phage is not deficient in int function. Prophage P2, on the other hand, is not excised from the host chromosome even in a derepressed lysogen unless int function is supplied by a superinfecting phage. Thus, the int function of P2 is expressed constitutively by the superinfecting phage, but is not expressed by the prophage even in the absence of phage repressor. It is proposed that the int function of P2 is not controlled by phage repressor, but belongs instead to a constitutive operon that is physically disrupted by prophage integration.
已知噬菌体P2中的原噬菌体整合以及相反的过程——原噬菌体切离，都需要一种特定的噬菌体基因产物，即所谓的整合酶（int）功能。我们发现，只要超感染噬菌体的整合酶功能不缺失，P2就能在免疫宿主（即存在噬菌体特异性阻遏物的情况下）的游离附着位点高效整合。另一方面，除非超感染噬菌体提供整合酶功能，否则原噬菌体P2即使在去阻遏的溶源菌中也不会从宿主染色体上切离。因此，P2的整合酶功能由超感染噬菌体组成型表达，但即使在没有噬菌体阻遏物的情况下，原噬菌体也不表达该功能。有人提出，P2的整合酶功能不受噬菌体阻遏物控制，而是属于一个组成型操纵子，该操纵子在原噬菌体整合时会被物理破坏。
