Transcription antitermination: the lambda paradigm updated.
Coliphage lambda employs systems of transcription termination and antitermination to regulate gene expression. Early gene expression is regulated by the phage-encoded N protein working with a series of Escherichia coli proteins, Nus, at RNA sites, NUT, to modify RNA polymerase to a termination-resistant form. Expression of lambda late genes is regulated by the phage-encoded Q antitermination protein. Q, which appears to use only one host factor, acts at a DNA site, qut, to modify RNA polymerase to a termination-resistant form. This review focuses on recent studies which show that: (i) N can mediate antitermination in vitro, independent of Nus proteins. (ii) Early genes in another lambdoid phage HK022 are also regulated by antitermination, where only an RNA signal appears necessary and sufficient to create a termination-resistant RNA polymerase. (iii) A part of the qut signal appears to be read from the non-template DNA strand. (iv) A host-encoded inhibitor of N antitermination appears to act through the NUT site as well as with the alpha subunit of RNA polymerase, and is antagonized by NusB protein.
Friedman
D I
DI
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109-620, USA. davidfri@umich.edu
Court
D L
DL
D010582:Bacteriophage lambda / Q000235:genetics*; D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000502:physiology; D015967:Gene Expression Regulation, Viral; D005814:Genes, Viral; D008969:Molecular Sequence Data; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000235:genetics; D054334:Viral Regulatory and Accessory Proteins / Q000235:genetics / Q000502:physiology
C059417:N protein, Bacteriophage lambda; C073501:Nun protein, Enterobacteria phage HK022; C066119:Q protein, Bacteriophage lambda; D014157:Transcription Factors; D014764:Viral Proteins; D054334:Viral Regulatory and Accessory Proteins; D012321:DNA-Directed RNA Polymerases