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Bacteriophage Nf DNA region controlling late transcription: structural and functional homology with bacteriophage phi 29.

ABSTRACT: The putative region for the control of late transcription of the Bacillus subtilis phage Nf has been identified by DNA sequence homology with the equivalent region of the evolutionary related phage phi 29. A similar arrangement of early and late promoters has been detected in the two phages, suggesting that viral transcription could be regulated in a similar way at late times of the infection. Transcription of late genes requires the presence of a viral early protein, gpF in phage Nf and p4 in phage phi 29, being the latter known to bind to a DNA region located upstream from the phage phi 29 late promoter. We have identified a DNA region located upstream from the putative late promoter of phage Nf that is probably involved in binding protein gpF. Furthermore, we show that the phage phi 29 protein p4 is able to bind to this region and activate transcription from the phage Nf putative late promoter. Sequence alignment has also revealed the existence of significant internal homology between the two early promoters contained in this region of each phage.

SUBMITTER: Nuez B

PROVIDER: S-EPMC309670 | biostudies-other | 1993 Jun

REPOSITORIES: biostudies-other

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Bacteriophage Nf DNA region controlling late transcription: structural and functional homology with bacteriophage phi 29.

Nuez B B Salas M M

Nucleic acids research 19930601 12

The putative region for the control of late transcription of the Bacillus subtilis phage Nf has been identified by DNA sequence homology with the equivalent region of the evolutionary related phage phi 29. A similar arrangement of early and late promoters has been detected in the two phages, suggesting that viral transcription could be regulated in a similar way at late times of the infection. Transcription of late genes requires the presence of a viral early protein, gpF in phage Nf and p4 in p ...[more]

PMID: 8332494

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Project description:Like many viruses, bacteriophage phi X174 packages its DNA genome into a procapsid that is assembled from structural intermediates and scaffolding proteins. The procapsid contains the structural proteins F, G and H, as well as the scaffolding proteins B and D. Provirions are formed by packaging of DNA together with the small internal J proteins, while losing at least some of the B scaffolding proteins. Eventually, loss of the D scaffolding proteins and the remaining B proteins leads to the formation of mature virions.phi X174 108S 'procapsids' have been purified in milligram quantities by removing 114S (mature virion) and 70S (abortive capsid) particles from crude lysates by differential precipitation with polyethylene glycol. 132S 'provirions' were purified on sucrose gradients in the presence of EDTA. Cryo-electron microscopy (cryo-EM) was used to obtain reconstructions of procapsids and provirions. Although these are very similar to each other, their structures differ greatly from that of the virion. The F and G proteins, whose atomic structures in virions were previously determined from X-ray crystallography, were fitted into the cryo-EM reconstructions. This showed that the pentamer of G proteins on each five-fold vertex changes its conformation only slightly during DNA packaging and maturation, whereas major tertiary and quaternary structural changes occur in the F protein. The procapsids and provirions were found to contain 120 copies of the D protein arranged as tetramers on the two-fold axes. DNA might enter procapsids through one of the 30 A diameter holes on the icosahedral three-fold axes.Combining cryo-EM image reconstruction and X-ray crystallography has revealed the major conformational changes that can occur in viral assembly. The function of the scaffolding proteins may be, in part, to support weak interactions between the structural proteins in the procapsids and to cover surfaces that are subsequently required for subunit-subunit interaction in the virion. The structures presented here are, therefore, analogous to chaperone proteins complexed with folding intermediates of a substrate.

Dataset Information

Bacteriophage Nf DNA region controlling late transcription: structural and functional homology with bacteriophage phi 29.

Publications

Bacteriophage Nf DNA region controlling late transcription: structural and functional homology with bacteriophage phi 29.

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