PMID:7714899

Citation	Hung, SC and Gottesman, ME (1995) Phage HK022 Nun protein arrests transcription on phage lambda DNA in vitro and competes with the phage lambda N antitermination protein. J. Mol. Biol. 247:428-42
Abstract	Phage HK022 Nun protein excludes phage lambda by terminating transcription near the lambda nut sites. We have established a purified in vitro system that reproduces the in vivo sequence and factor requirements of Nun. Nun arrests transcription by E. coli RNA polymerase at or near elongation pause sites distal to the nut sites. The boxB sequence of nut is required for optimal Nun activity; boxA plays a lesser role. The efficiency of transcription arrest is strongly enhanced by the four E. coli Nus factors. The factors increase the specific activity of Nun, and allow it to act at higher ribonucleoside triphosphate concentrations. A wild-type boxA is required for stimulation by Nus factors. Nun and the lambda N antitermination protein compete for their opposing reactions. This competition may be at the level of binding of boxB RNA.
Links	PubMed
Keywords	Bacterial Proteins/metabolism; Bacterial Proteins/physiology; Bacteriophage lambda/genetics; Base Sequence; Binding, Competitive; Coliphages/genetics; Coliphages/physiology; DNA, Viral/genetics; DNA, Viral/metabolism; DNA-Directed RNA Polymerases/metabolism; Escherichia coli/metabolism; Escherichia coli/virology; Escherichia coli Proteins; Gene Expression Regulation, Viral; Molecular Sequence Data; Mutagenesis, Site-Directed; Nucleic Acid Conformation; Peptide Elongation Factors/physiology; Regulatory Sequences, Nucleic Acid; Ribosomal Proteins/physiology; Transcription Factors/physiology; Transcription, Genetic; Transcriptional Elongation Factors; Viral Interference/physiology; Viral Proteins/physiology
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
BPHK0:VNUN		GO:0006353: DNA-templated transcription, termination	ECO:0000314:		P		Figure 2 - In an in vitro system with RNA polymerase and the nun protein, increasing concentration of nun correlated with increasing amounts of relatively shorter RNA transcripts. (Data not shown) - Adding the nun protein after completion of transcription did not shorten RNA transcripts. Thus, its unlikely nun acts by cleaving or processing RNA transcripts. Figure 3A - Without nun, RNA polymerase transcription would only pause at certain lengths of RNA, before resuming activity again. However in presence of nun, transcription would completely be completely blocked without resuming again once these similar length RNA transcripts were reached. Both with and without nun, similar length RNA transcripts would appear at similar times. Figure 3B - Next, the authors separated the the RNA transcript products onto a gel. They found that the sites that nun acted on and the sites where RNA polymerase paused were either identical or extremely close in proximity. All these results taken into consideration suggest nun arrests transcription by directly acting at RNA polymerase pause sites.	complete CACAO 12477

References

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