Overexpression of phage HK022 Nun protein is toxic for Escherichia coli.
The Nun protein of coliphage HK022 excludes superinfecting lambda phage. Nun recognizes and binds to the N utilization (nut) sites on phage lambda nascent RNA and induces transcription termination. Overexpression of Nun from a high-copy plasmid is toxic for Escherichia coli, despite the fact that nut sites are not encoded in the E. coli genome. Cells expressing Nun cannot exit stationary phase. Toxicity is related to transcription termination, since host and nun mutations that block termination also suppress cell killing. Nun inhibits expression of wild-type lacZ, but not lacZ expressed from the Crp/cAMP-independent lacUV5 promoter. Microarray and proteomic analyses show that Nun down-regulates crp and tnaA. Crp overexpression and high indole concentrations partially reverse Nun-mediated toxicity and restore lacZ expression.
Institute of Cancer Research, Columbia University Medical Center, New York, NY 10032, USA.
Augusto
A
Uc-Mass
Arkady
A
Khodursky
Lewis
L
Brown
Max E
ME
Gottesman
D025523:Bacteriophage HK022 / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D007211:Indoles / Q000032:analysis / Q000378:metabolism; D007763:Lac Operon / Q000235:genetics; D009154:Mutation; D011401:Promoter Regions, Genetic; D013728:Terminator Regions, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics / Q000378:metabolism* / Q000633:toxicity*
D007211:Indoles; C073501:Nun protein, Enterobacteria phage HK022; D014157:Transcription Factors; D014764:Viral Proteins; C030374:indole