Ghelardini P, La Valle R, Paolozzi L
Centro Acidi Nucleici del CNR, Roma, Italy.
Genetica. 1994;94(2-3):151-6. doi: 10.1007/BF01443429.
Two genes, gemA and gemB, belong to the gem operon located in the semi-essential early region of bacteriophage Mu. The product of gemA modulates the expression of various host genes, including cell division and DNA replication genes. In addition, GemA is also responsible for decreasing host DNA gyrase activity and for DNA relaxation. The product of gemB is involved in Mu late gene transcriptional transactivation. Phage mutants such as Mu gem2ts have strong effects on the bacterial host: i) infected bacteria become unable to grow in minimal synthetic medium and behave phenotypically as relA- mutants; ii) survivors of the infection are re-programmed in their cell cycles, with synchronous cell divisions, cyclical waves of DNA relaxation and recoiling and; iii) Mu gem2ts prophages excise precisely their DNA from the initial integration site and re-integrate in other non-randomly distributed sites. Neither the phage transposase nor the host RecA protein are implicated in this process.
两个基因，gemA和gemB，属于位于噬菌体Mu半必需早期区域的gem操纵子。gemA的产物调节各种宿主基因的表达，包括细胞分裂和DNA复制基因。此外，GemA还负责降低宿主DNA促旋酶活性并使DNA松弛。gemB的产物参与Mu晚期基因的转录反式激活。诸如Mu gem2ts之类的噬菌体突变体对细菌宿主有强烈影响：i）受感染的细菌在基本合成培养基中无法生长，并且在表型上表现为relA-突变体；ii）感染的幸存者在其细胞周期中被重新编程，具有同步细胞分裂、DNA松弛和重新卷曲的周期性波动；iii）Mu gem2ts原噬菌体从初始整合位点精确切除其DNA并重新整合到其他非随机分布的位点。噬菌体转座酶和宿主RecA蛋白均不参与此过程。
