Phage HK022 Nun protein represses translation of phage lambda N (transcription termination/translation repression).
The N-terminal arginine-rich motif of phage HK022 Nun protein binds to NUT sequences in phage lambda nascent transcripts and induces transcription termination. Interactions between the Nun C terminus and RNA polymerase as well as the DNA template are required for termination. We have isolated Nun C-terminal point and deletion mutants that are unable to block transcription. The mutants bind NUT RNA and inhibit translation of the lambda N gene. Thus HK022 excludes lambda both by terminating transcription on the phage chromosome and by preventing translation of the essential lambda N gene. Like N autoregulation, translation repression by Nun requires host RNaseIII deficiency (rnc) or a mutation in the RNaseIII processing site (rIII) located between NUTL and the beginning of the N coding sequence. Our data support the idea that Nun bound at NUTL causes steric interference with ribosome attachment to the nearby N coding sequence. Two models, Nun acting alone or in complex with host proteins, are discussed.
Kim
Hyeong C
HC
Department of Biochemistry and Molecular Biophysics, and Institute of Cancer Research, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
Zhou
Jian-guang
JG
Wilson
Helen R
HR
Mogilnitskiy
Grigoriy
G
Court
Donald L
DL
Gottesman
Max E
ME
D010582:Bacteriophage lambda / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D009154:Mutation; D009690:Nucleic Acid Conformation; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D013728:Terminator Regions, Genetic; D014764:Viral Proteins / Q000502:physiology*
D017931:DNA Primers; D012333:RNA, Messenger; D014764:Viral Proteins