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Unformatted text preview: The EMBO Journal Vol.16 No.19 pp.5914–5921, 1997 Transcriptional silencing by the mycobacteriophage L5 repressor has a gene organization that is reminiscent of phage Kelly L.Brown, Gary J.Sarkis 1 , lambda (Hatfull and Sarkis, 1993). However, in L5 the Curtis Wadsworth and Graham F.Hatfull 2 early lytic genes in the right arm are all transcribed Department of Biological Sciences, University of Pittsburgh, leftwards (see Figure 5), in contrast to the divergent Pittsburgh, PA 15260 and 1 Department of Molecular Biophysics and transcription in lambda from the P L and P R promoters Biochemistry, Yale University, New Haven, CT 06510, USA flanking the repressor gene (Hendrix et al. , 1983; Hatfull 2 Corresponding author and Sarkis, 1993). In both phages, the structural genes in e-mail: GFH@vms.cis.pitt.edu the left arm are transcribed rightwards late in lytic growth (Hendrix et al. , 1983; Hatfull and Sarkis, 1993; Hatfull The success of a temperate bacteriophage is dependent and Jacobs, 1994). upon its ability to completely shut down expression of Genetic experiments suggest that L5 gene 71 encodes its lytic genes during lysogenic growth. Mycobacterio- the phage repressor (gp71) since it is required for the phage L5 accomplishes this by an atypical phage maintenance of lysogeny and also confers superinfection repressor, gp71, which binds to multiple asymmetric immunity (Donnelly-Wu et al. , 1993). The early lytic DNA sites. L5 gp71 regulates transcription initiation promoter P left (see Figure 5) is a good candidate for direct at an early lytic promoter, P left , but also affects down- regulation by gp71, since it is inactive during lysogeny stream gene expression at ‘stoperator’ sites in the phage and induced early in lytic growth (Nesbit et al. , 1995); genome. The L5 genome is replete with stoperator sites no other early lytic promoters have been identified, and located within short intergenic spaces in both the early P left may be responsible for initiating all early lytic and late lytic operons and oriented specifically with transcription (Nesbit et al. , 1995). In addition to 71 , there respect to transcription. Binding of gp71 to these sites appears to be at least one other gene that influences results in a strong orientation-dependent polar effect lysogenic frequencies that is as yet unmapped (Donnelly- on downstream gene expression and global silencing Wu et al. , 1993; Sarkis et al. , 1995). L5 does not encode of prophage gene expression. its own RNA polymerase and utilizes the host RNA Keywords : bacteriophage/mycobacteria/repressor/ polymerase for both early and late lytic gene expression transcription/tuberculosis (Hatfull and Sarkis, 1993)....
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This note was uploaded on 01/23/2011 for the course CMPS 003 taught by Professor Gerald during the Spring '10 term at University of California, Santa Cruz.
- Spring '10