Transcription termination sites in the major leftward operon of coliphage lambda

Salstrom, John S.; Szybalski, Waclaw

doi:10.1016/0042-6822(78)90282-9

Cited by 47 publications

(8 citation statements)

References 26 publications

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“…Positive regulation of X gene expression by N involves suppression of several Rho-dependent and Rho-independent terminators (5,25). The antitermination of either class of terminators by N involves both NusA and NusB proteins, which are required in approximately equimolar ratio (16,18).…”

Section: Resultsmentioning

confidence: 99%

Evidence that ribosomal protein S10 itself is a cellular component necessary for transcription antitermination by phage lambda N protein.

Das¹,

Ghosh²,

Barik³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

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Bacteriophage X N gene product acts to modify host RNA polymerase allowing the formation of a termination-resistant transcription apparatus. Previous studies have demonstrated that the nusE71 mutation that has altered the ribosomal protein S10 prevents N action in vivo. Using a coupled transcription-translation system, we demonstrate here that purified S10 protein as well as the 30S ribosomal subunit is sufficient to restore N activity in the nusE mutant extract, allowing antitermination of Rho-dependent and Rho-independent terminators. This provides direct biochemical evidence that the S10 protein itself is one of the cellular components necessary for the formation of an antitermination apparatus.

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Section: Resultsmentioning

confidence: 99%

Evidence that ribosomal protein S10 itself is a cellular component necessary for transcription antitermination by phage lambda N protein.

Das¹,

Ghosh²,

Barik³

et al. 1985

Proc. Natl. Acad. Sci. U.S.A.

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“…To achieve expression of the clII gene independently of other phage proteins, we constructed the plasmid ptacclll, consisting of a 450-bp X DNA fragment carrying the clII gene cloned downstream of the tac promoter of the expression vector pKK223-3 (see Materials and Methods). The cloned fragment harbors, in addition to clII, 220 bp of upstream sequences, including the 3' end of the ssb gene and the tL2b transcription terminator (28,37), and 55 bp downstream of cIII (Fig. 1A).…”

Section: Resultsmentioning

confidence: 99%

Genetic analysis of bacteriophage lambda cIII gene: mRNA structural requirements for translation initiation

et al. 1989

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The bacteriophage A cIl gene product regulates the lysogenic pathway. The cIl gene is located in the leftward operon, which is transcribed from the PL promoter. We have previously shown (S. Altuvia and A. B. Oppenheim, J. Bacteriol. 167:415-419, 1986) that mutations that show elevated expression lie within the clll coding sequence. We isolated mutants that show decreased CIII activity. AUl the mutations were found to cause a drastic reduction in the rate of initiation of cHl translation. Several mutations were found to be scattered within the first 40 nucleotides of the cIl coding region. Additional mutations affected the AUG initiation codon, the Shine-Dalgarno sequence, and the upstream RNaseIII processing site. Computer folding of the cIl mRNA suggested the presence of two alternative RNA structures. All the mutations within the coding region that reduce expression reduce the stability of one specific mRNA structure (structure B). Mutations that increase expression lie in the loops of this structure and may in fact stabilize it by interfering with the formation of the alternative structure (structure A). Thus, it appears that a specific mRNA secondary structure at the beginning of the cIl coding region is essential for efficient translation, suggesting that changes in mRNA structure regulate cm expression.Initiation of translation in procaryotes has been intensively investigated (for recent reviews, see references 14 and 42). Some structural elements important for mRNA recognition by the ribosome have been defined, namely, the Shine-Dalgarno sequence (39), the initiation codon, the spacing between these two elements, and other nonrandomly occurring nucleotides before and after the initiation codon (e.g., see reference 20).Many experiments also suggested that, to be available for ribosome recognition, the ribosome-binding region must be free of occluding secondary structures that may block ribosome access; i.e., it must either be located in a region free of secondary structures or be located in a hairpin loop (14,17,22,46). There are examples in which opening of such an joccluding secondary structure by incoming ribosomes is used to achieve translational coupling between bacteriophage genes (6, 8). In other cases, alternative mRNA structures have been proposed as a way to control expression of drug resistance genes (11,31,33).Infection of Escherichia coli by bacteriophage X may lead to a lytic or a lysogenic response (18). In the lysogenic response, cll and cIII gene products play a critical role. The cll gene product acts as a positive regulator and activates several phage promoters (12,47). It is a highly unstable protein with a half-life of 1.5 min (16). The clll gene product, a 54-amino-acid-long protein (25), was found to stabilize the CII protein in vivo, extending its half-life (19,34). It was also found to induce the heat shock response, probably through stabilization of C&32 (3). Phage mutants defective in the clll gene lysogenize poorly (24), whereas elevated expression of CIII caused by point mutat...

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“…4) which is followed by a row of five uridines; this type ofstructure is characteristic oftranscription terminators. N protein-modified polymerases which initiate at the PL promoter transcribe through such termination signals (40,44). At this site, the elongated PL transcript can adopt a new form similar to that of substrates for RNase III (45).…”

Section: (37)mentioning

confidence: 99%

Posttranscriptional control of bacteriophage lambda gene expression from a site distal to the gene.

Guarneros¹,

Montañéz²,

Hernández³

et al. 1982

Proc. Natl. Acad. Sci. U.S.A.

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The bacteriophage A int gene product, integrase, recombines the phage DNA with the host DNA at specific sites on each to accomplish lysogeny. The int gene is transcribed from two promoters, PL and PI, each regulated positively by A proteins. The expression of integrase is also controlled from a site, sib, in the b region of the phage genome. This is a unique regulatory site because it is located distal to the structural gene in relation to the promoters. The expression ofint from the PL promoter is inhibited when sib is present. This effect appears to be specific for PL because sib does not cause inhibition of PI-dependent int synthesis.A mutants that contain alterations in the site have been isolated. Sequence analyses of the mutations reveal single base changes, spanning 37 base pairs (bp) in the b region, some 240-bp beyond the int gene. Another mutant, hef13, which has a phenotype similar to that of sib, introduces a nucleotide change within the same 37-bp region. The sib and hefmutatsons cluster within a region of dyad symmetry. Regulation of int synthesis by sib occurs after transcription.of the int gene. There is no difference in the rate of .PL'promoted int mRNA synthesis in either sib' or sib-phage infections, yet int mRNA is less stable in the sib' infection. Because RNase 111 host mutants are defective in sib regulation, processing of the PL mRNA at sib by this endoribonuclease may cause int mRNA decay and decrease int synthesis.Bacteriophage A inserts its DNA into the Escherichia coli chromosome as part of the process leading to lysogeny. This integration event uses A int protein and occurs by reciprocal recombination at specific locations, named "attachment sites," in the phage (attP) and in the bacterial (attB) DNAs. The reversal of the integrative reaction is excision; this process occurs after prophage induction and allows the integrated DNA to dissociate from the bacterial chromosome. The two phage proteins int and xis are required for excisive recombination. Host factors are also required for both integration and excision, but the direction of the reaction depends primarily upon the presence of int or int and xis in the cell (1-3).Two promoters, PI and PL, control transcription of the 1.5-kilobase int-xis region (4, 5) (Fig. 1). Both promoters are positively regulated by different effectors. Gene N product allows elongation of the PL transcript through several genes into the int-xis region (11,12). The cII product is required to initiate transcription from PI by facilitating initiation by RNA polymerase (7). The PI promoter overlaps with the xis gene, and its transcript does not include all of xis (8-10). Thus a differential expression of the integration and excision systems is assured by turning on and off PI or PL Infections with cII-phage result in decreased int protein levels and integration activity (13)(14)(15). This result is unexpected because transcription initiated by RNA polymerase at PL was thought to extend through thexis-int region (11, 16). However, infection with b2cII-...

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Transcription termination sites in the major leftward operon of coliphage lambda

Cited by 47 publications

References 26 publications

Evidence that ribosomal protein S10 itself is a cellular component necessary for transcription antitermination by phage lambda N protein.

Evidence that ribosomal protein S10 itself is a cellular component necessary for transcription antitermination by phage lambda N protein.

Genetic analysis of bacteriophage lambda cIII gene: mRNA structural requirements for translation initiation

Posttranscriptional control of bacteriophage lambda gene expression from a site distal to the gene.

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