Transcription activation at Class I CAP‐dependent promoters

Ebright, Richard H.

doi:10.1111/j.1365-2958.1993.tb01626.x

Cited by 247 publications

(209 citation statements)

References 54 publications

(16 reference statements)

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“…The architecture of the yfiD promoter is therefore unlike any other previously analysed FNR-activated promoter (Guest et al, 1996) and the contribution of each FNR site to the overall regulation of yfiD expression is being investigated. The genes regulated by the CRP/ FNR family can be grouped into three classes based on ᮊ 1997 Blackwell Science Ltd, Molecular Microbiology, 24, 593-605 the position of the DNA site for the regulator and the requirements for transcription activation (Ebright, 1993). Class I promoters have CRP/FNR sites centred at or near ¹61.5, ¹72.5, ¹82.5 or ¹92.5, and thus the yfiD promoter is a variant of the Class I type.…”

Section: Discussionmentioning

confidence: 99%

HlyX, the FNR homologue of Actinobacillus pleuropneumoniae, is a [4Fe–4S]‐containing oxygen‐responsive transcription regulator that anaerobically activates FNR‐dependent Class I promoters via an enhanced AR1 contact

Green

Baldwin

1997

Molecular Microbiology

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SummaryThe hlyX gene of the pig pathogen Actinobacillus pleuropneumoniae encodes HlyX, a homologue of FNR, the anaerobic transcription regulator of Escherichia coli. The hlyX gene complements the anaerobic respiratory deficiencies of E. coli fnr mutants but also induces the expression of an otherwise latent haemolysin. Therefore, FNR and HlyX have distinct but overlapping regulons. The hlyX gene has been overexpressed as a gst ::hlyX fusion and the HlyX protein purified. Similar to FNR, HlyX can acquire a [4Fe-4S] cluster, which promotes binding to the FNR box (K d of 20-30 nM) under anaerobic conditions. Expression of hlyX in E. coli induced the anaerobic production of at least five polypeptides, including the yfiD gene product, which were not induced by fnr. Analysis of the yfiD promoter region revealed the presence of two FNR boxes situated at ¹61.5 and ¹114.5. Consistent with this observation, expression from the semi-synthetic Class I promoter FFþ20pmelR was efficiently activated by HlyX but not by FNR. The weaker level of FNRmediated activation of Class I promoters suggests that there is a poorer activating contact (activating region 1 (AR1) equivalent) between FNR and RNA polymerase at these promoters and that HlyX possesses an additional or improved AR1. The AR1 of HlyX is partially characterized by a surface-exposed region around amino acid A187, which confers the altered specificity and provides an explanation for the existence of distinct but overlapping HlyX and FNR regulons.

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Section: Discussionmentioning

confidence: 99%

HlyX, the FNR homologue of Actinobacillus pleuropneumoniae, is a [4Fe–4S]‐containing oxygen‐responsive transcription regulator that anaerobically activates FNR‐dependent Class I promoters via an enhanced AR1 contact

Green

Baldwin

1997

Molecular Microbiology

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“…The AR1 contact between regulator RNA polymerase is a feature of both Class I and Class I1 promoters (Savery et al, 1996). For CRP at Class I1 promoters the role of the AR1 contact is that of anti-inhibition (Niu et al, 1996), whereas at Class I promoters AR1 makes an activating contact with the a subunit of RNA polymerase (Ebright, 1993). The results obtained with FNR-R184P suggest that the AR1 contact at Class I promoters (FNR contacts the downstream a subunit of RNA polymerase) may not be identical to that at Class I1 promoters (FNR contacts the upstream a subunit) and that R184 may be more involved in making an anti-inhibition (Class 11) rather than an activating contact (Class I).…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, as the position of the FNR-binding site at the hZyE promoter is always beyond -41, hZyE is a Class I promoter (Ebright, 1993).…”

Section: The My€ Promoter Contains An Fnr Site and Is Differentially mentioning

confidence: 99%

The molecular basis for the differential regulation of the hlyE-encoded haemolysin of Escherichia coli by FNR and HlyX lies in the improved Activating Region 1 contact of HlyX

Green

Baldwin

1997

Microbiology

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The regulator of fumarate and nitrate reduction (FNR) protein of Escherichia coli is an oxygen-responsive transcription regulator that acts mainly to activate the transcription of genes associated with anaerobic energy generation during periods of oxygen starvation. The hlyX gene of the swine pathogen Actinobacillus pleuropneumoniae encodes an FNR homologue, HlyX, which can complement the anaerobic respiratory deficiencies of an fnr mutant. However, FNR and HlyX have distinct but overlapping regulons because during anaerobic incubation, hlyX-expressing Em coli K-12 strains produce an otherwise latent haemolysin. The gene encoding the 'latent' haemolysin has been designated hlyE and analysis of the promoter region by DNase I footprinting reveals the presence of an FNR-(HlyX-) binding site. Anaerobic expression of an hlyE: :lac2 reporter was 6.5-fold higher in hlyX compared to fnr-expressing cells. Both FNR and HlyX recruited RNA polymerase to the hlyE promoter but formed different ternary complexes. One major transcript (tspl) initiating a t 78.5 bp downstream of the FNR-binding site and four minor transcripts initiating a t 73-5 (tsp2), 71.5 (tsp3), 63.5 (tsp4) and 62-5 (tsp5) bp from the FNR site were detected. From the position of the FNR box relative to the transcript starts, hlyE is expressed from a Class I FNR-regulated promoter. Substitution of selected FNR amino acids with the residues found in the equivalent positions in HlyX indicated that Activating Region 1 (AR1) of FNR forms a surface encompassing Ps to pl1 and that the AR1 contact a t Class I promoters is different to that a t Class II promoters, although the same surface is involved. The FNR variant, FNR-A225T, combined the properties of FNR (good activation from Class II promoters) and HlyX (good activation of Class I promoters) and conferred the haemolytic phenotype.

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“…In E. coli, the CRPdependent promoters are grouped into three classes. Class I has a single CRP-binding site, centred at one of the positions 261?5, 271?5, 281?5 or 291?5; class II possesses a CRPrecognition site centred at 241?5, which thus overlaps with the 235 sequence; and class III requires two or more CRPbinding sites in the promoter for full activation (Busby & Ebright, 1999;Ebright, 1993;Ushida & Aiba, 1990). Based on the position of the CRP-recognition sequence 258?5 nt upstream of the TSP, the M. tuberculosis whiB1 promoter region most resembles the class I CRP-dependent promoters of E. coli.…”

Section: Discussionmentioning

confidence: 99%

Regulation of the expression of whiB1 in Mycobacterium tuberculosis: role of cAMP receptor protein

2006

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The wbl (whiB-like) genes encode putative transcription factors unique to actinomycetes. This study characterized the promoter element of one of the seven wbl genes of Mycobacterium tuberculosis, whiB1 (Rv3219c). The results reveal that whiB1 is transcribed by a class I-type cAMP receptor protein (CRP)-dependent promoter, harbouring a CRP-binding site positioned at "58?5 with respect to its transcription start point. In vivo promoter activity analysis and electrophoretic mobility shift assays suggest that the expression of whiB1 is indeed regulated by cAMP-dependent binding of CRP M (encoded by the M. tuberculosis gene Rv3676) to the whiB1 59 untranslated region (59UTR). b-Galactosidase gene fusion analysis revealed induction of the whiB1 promoter in M. tuberculosis on addition of exogenous dibutyric cAMP (a diffusible cAMP analogue) only when an intact CRP-binding site was present. These results indicate that M. tuberculosis whiB1 transcription is regulated in part by cAMP levels via direct binding of cAMP-activated CRP M to a consensus CRP-binding site in the whiB1 59UTR. INTRODUCTIONMycobacterium tuberculosis, the aetiological agent of tuberculosis, accounts for nearly 2 million human deaths every year. Approximately one-third of the world's population is latently infected with M. tuberculosis, and 7 to 8 million new TB cases occur annually (Dye et al., 1999). M. tuberculosis can survive in diverse surroundings ranging from the human host to droplet nuclei in the atmosphere. Adaptation to such diverse conditions requires controlled regulation of the expression of key genes that allow the bacillus to alter its physiology in response to changes in environmental stimuli. Sequencing of the M. tuberculosis genome has revealed the presence of more than 100 regulatory proteins, 13 sigma factors and 11 two-component systems (Cole et al., 1998), which provide the bacterium with a high degree of adaptability.The Wbl (WhiB-like) family of proteins is present throughout the actinomycetes but absent from all other organisms evaluated so far (Molle et al., 2000;Soliveri et al., 2000). Due to the presence of a conserved helix-turn-helix motif, these proteins are believed to function as DNA-binding transcription regulators. The first of these proteins, WhiB, was identified in Streptomyces coelicolor, a Gram-positive sporulating bacterium closely related to M. tuberculosis. S. coelicolor whiB mutants produce abnormally long, tightly coiled aerial hyphae that are completely blocked in their ability to form sporulation septa (Chater, 1972;Davis & Chater, 1992;Flardh et al., 1999). Studies of whiB orthologues in mycobacteria have shown that the M. smegmatis whiB2 gene (also called whmD) is essential ; M. tuberculosis whiB3 plays a role in virulence and its gene product may interact with a sigma factor of RNA polymerase (Steyn et al., 2002); whiB7 of M. tuberculosis is involved in multi-drug resistance (Morris et al., 2005). Each of the Wbl family of proteins contains four invariant cysteine residues, which are believed to be inv...

show abstract

Transcription activation at Class I CAP‐dependent promoters

Cited by 247 publications

References 54 publications

HlyX, the FNR homologue of Actinobacillus pleuropneumoniae, is a [4Fe–4S]‐containing oxygen‐responsive transcription regulator that anaerobically activates FNR‐dependent Class I promoters via an enhanced AR1 contact

HlyX, the FNR homologue of Actinobacillus pleuropneumoniae, is a [4Fe–4S]‐containing oxygen‐responsive transcription regulator that anaerobically activates FNR‐dependent Class I promoters via an enhanced AR1 contact

The molecular basis for the differential regulation of the hlyE-encoded haemolysin of Escherichia coli by FNR and HlyX lies in the improved Activating Region 1 contact of HlyX

Regulation of the expression of whiB1 in Mycobacterium tuberculosis: role of cAMP receptor protein

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