Giusti M, Di Lallo G, Ghelardini P, Paolozzi L
Centro Acidi Nucleici del C.N.R. Roma, Italy.
Virology. 1990 Dec;179(2):694-700. doi: 10.1016/0042-6822(90)90136-f.
The gem product of bacteriophage Mu modulates synthesis of various host proteins and alters the host chromosome topology. To elucidate the role of the gem gene in Mu development, we analyzed the behavior of several mutants in this gene. The results, obtained with two Mu gem- phages, show that (1) phage growth is significantly delayed and inhibited, (2) early transcription is normal but late transcription is delayed and reduced, (3) DNA replication appears normal, and (4) the Mu C gene, whose product positively regulates Mu late genes, is one of the gem target sites. Transcription of a C promoter-lacZ fusion, carried by the pPH91 plasmid, is stimulated both after infection with Mu gem+ or Mu gem3 and is strains lysogenic for the same phages in the presence of viral immunity. These data suggest that the primary role of the gem product is modulation of gene expression. This control could be carried out by direct interaction with transcription factors or by changing DNA supercoiling.
噬菌体Mu的gem产物可调节多种宿主蛋白的合成并改变宿主染色体拓扑结构。为阐明gem基因在Mu发育中的作用，我们分析了该基因中几个突变体的行为。用两种Mu gem-噬菌体获得的结果表明：（1）噬菌体生长显著延迟并受到抑制；（2）早期转录正常，但晚期转录延迟且减少；（3）DNA复制似乎正常；（4）其产物正向调节Mu晚期基因的Mu C基因是gem的靶位点之一。由pPH91质粒携带的C启动子-lacZ融合基因的转录，在感染Mu gem+或Mu gem3后以及在病毒免疫存在下，对于溶原性相同噬菌体的菌株均受到刺激。这些数据表明，gem产物的主要作用是调节基因表达。这种调控可能通过与转录因子直接相互作用或通过改变DNA超螺旋来实现。
