The complex pattern of transcription in the segment of the bacteriophage T4 genome containing three of the head protein genes (original) (raw)
Related papers
Transcription of the T4 late genes
Virology Journal, 2010
This article reviews the current state of understanding of the regulated transcription of the bacteriophage T4 late genes, with a focus on the underlying biochemical mechanisms, which turn out to be unique to the T4-related family of phages or significantly different from other bacterial systems. The activator of T4 late transcription is the gene 45 protein (gp45), the sliding clamp of the T4 replisome. Gp45 becomes topologically linked to DNA through the action of its clamp-loader, but it is not site-specifically DNA-bound, as other transcriptional activators are. Gp45 facilitates RNA polymerase recruitment to late promoters by interacting with two phage-encoded polymerase subunits: gp33, the co-activator of T4 late transcription; and gp55, the T4 late promoter recognition protein. The emphasis of this account is on the sites and mechanisms of actions of these three proteins, and on their roles in the formation of transcription-ready open T4 late promoter complexes.
Virology, 1989
Eight 5' ends of RNA molecules which encompass the bacteriophage T4 base plate late genes 51 to 26 region have been mapped by Sl nuclease protection and reverse transcription within a 246-bp DNA segment. Two of eight 5'ends are initiated at two absolutely conserved late promoter sites, P51 and P26a, that direct RNA synthesis on opposite strands. These two promoters share four of eight promoter sequence base pairs. A third 5' end arises from another promoter, P26b, which shows one base pair mismatch with respect to the absolutely conserved-10 sequence. All the other 5' ends arise from RNA processing and/or degradation. Since no other late transcription promoter sites were found within the base plate cluster sequence, we propose that the two overlapping late promoters, P51 and P26a, direct the expression of the T4 base plate gene cluster, included between map coordinates 114,000 and 121,038: P51 directs the transcription of genes 51, 27, 28, 29, 48, and 54 on the r DNA strand and P26a the transcription of genes 26 and 25 on the I DNA strand. This peculiar promoter configuration might account for the low level of transcription of these late genes.
Mapping of Promoter Sites on the Genome of Bacteriophage M13
European Journal of Biochemistry, 1976
With the aid of transcription studies on restriction fragments of bacteriophage M13 DNA it has been demonstrated that at least eight promoter sites are located on the M13 genome. Five of these promoters initiate the synthesis of RNA chains which contain at their 5'-terminal end pppG (G promoters), while the other three promoters initiate RNA chains which start exclusively with pppA (A promoters). The positions of these promoter sites on the physical map are : 0.82 (G0.82), 0.88 0.94 (G0.94), 0.01 (Go.oI), 0.08 (G 0. 0 8) , 0.36 (A0.36), 0.51 (A0.51) and 0.56 (A0.56). The G promoters were found to be clustered within a distance of one-third of the genome length from the central termination site for transcription (map position 0.77). The A promoters, however, were found at greater distances from this termination signal. Based upon the incorporation of [y-32P]ATP or [ Y-~~P I G T P , the capacity of these promoters to initiate the synthesis of RNA chains varies. The strongest G promoters are G0.82, G0.94 and G0.08 and the strongest A promoter is A0.36. As judged from their position on the genetic map, it is postulated that two promoters, namely G0.94 and Go.01, are located within gene 11. The other promoters are most probably located immediately in front of the gene VIII/VII boundary (Go.xz), and immediately in front of gene V gene I1 (G0.08), gene IV (A0.36), gene I (A0.51) and gene VI (A0.56). No evidence has been obtained so far for the existence of a promoter immediately in front of gene 111.
Proceedings of the National Academy of Sciences, 1976
T-even coliphages have 5-hydroxymethylcytosine in their DNA instead of cylosine. In some T4 mutants, the replicated DNA contains cytosine, but then no late gene products are made. We show that the inability to make late gene products with cytosine-containing T4 DNA is due to a T4 gene product. This gene product, while probably nonessential under normal conditions, interacts with an essential part of the transcription apparatus. Mutations in this gene allow viable T4 particles to be made whose DNA has been substituted almost 100% with cytosine.
Regulation of a bacteriophage T4 late gene, soc, which maps in an early region
Genetics, 1984
We have sequenced and analyzed the expression of an early region of the bacteriophage T4 genome that surprisingly contains a late gene, soc. soc is oriented in the same direction as early genes, like the T4 lysozyme gene. Northern hybridization of early and late T4 RNA, using cloned T4 restriction fragments as probes, identified two long early transcripts and a short late transcript, all containing the soc-coding sequence. Thus, soc is transcribed both early and late. It is, however, translated only late. The inhibition of soc translation from the long early transcripts can be explained by formation of a hairpin in the RNA that sequesters the soc ribosome-binding site. The transcript initiated at the late promoter cannot form this hairpin and is, therefore, translated.
Identification of Upstream Sequences Essential for Activation of a Bacteriophage P2 Late Promoter
Journal of Bacteriology, 2003
We have carried out a mutational scan of the upstream region of the bacteriophage P2 FETUD late operon promoter, P F , which spans an element of hyphenated dyad symmetry that is conserved among all six of the P2 and P4 late promoters. All mutants were assayed for activation by P4 Delta in vivo, by using a lacZ reporter plasmid, and a subset of mutants was assayed in vitro for Delta binding. The results confirm the critical role of the three complementary nucleotides in each half site of the upstream element for transcription factor binding and for activation of transcription. A trinucleotide DNA recognition site is consistent with a model in which these transcription factors bind via a zinc finger motif. The mutational scan also led to identification of the ؊35 region of the promoter. Introduction of a 70 ؊35 consensus sequence resulted in increased constitutive expression, which could be further stimulated by Delta. These results indicate that activator binding to the upstream region of P2 late promoters compensates in part for poor 70 contacts and helps to recruit RNA polymerase holoenzyme.
Nuckotide sequence of the three major early promoters of bacteriophage T7
Nucleic Acids Research, 1979
I have determined the nucleotide sequences of the three major early promoters of bacteriophage T7 (Al, A2, A3). The sequences confirm the two main homologies found between other known promoters for E. coli RNA polymerase (nucleoside triphosphate:RNA nucleotidyl transferase, E.C. 2.7.7.6). In particular, all three T7 promoters show a very good match with the -35 region homology; the A2 and A3 promoters share a 17 basepair sequence in this region. On the other hand, the match with the Pribnow Box homology is much less pronounced and different for each T7 promoter.