Catabolite repression-resistant mutations of the Bacillus subtilis alpha-amylase promoter affect transcription levels and are in an operator-like sequence

Carbon Catabolite Control of the Metabolic Network inBacillus subtilis

“…CCR of the gnt operon carrying a cre in the gntR-coding region is partially promoterindependent, and the amounts of the transcripts containing regions downstream of the cre decrease considerably on the addition of glucose, 7) implying that transcriptional roadblock might be involved in this catabolite repression. This is supported by the finding 88) that a mutation of mfd encoding a transcription-repair coupling factor, Mfd, 89) relieves CCR of hut and gnt expression at the cis-acting cre sequences located downstream of their transcriptional start sites, but does not affect CCR at the promoter-proximal cre sites, such as in amyE 3) and bglP, 27) suggesting that the Mfd protein displaces RNA polymerase stalled at downstream cre sites to which the CcpA/P-Ser-HPr (or -Crh) is bound. Nonetheless, CCR of acsA expression is not affected by an mfd mutation in spite of the location of the acsA cre 44 bp downstream of the acsA transcriptional initiation sites, but CCR is relieved by it if the cre is placed 161 bp downstream of the initiation site.…”

“…Nearly 20 years ago, pioneering work on CCR of -amylase synthesis in B. subtilis resulted in the identification of two constituents of the major catabolite control mechanism: a 14-bp cis-acting palindromic sequence (TGTAAGCGTTAACA) subsequently called the catabolite-responsive element (cre) for amyE located in the promoter region of amyE, 3,4) and the CcpA protein, a member of the LacI/GalR family of transcriptional regulators. 5) Mutations in either of these constituents resulted in relief from CCR of amyE expression.…”

“…The CcpA/P-Ser-HPr (or P-Ser-Crh) complex binds to a cre overlapping the promoter, interfering with the binding of the transcription machinery, as for amyE, 3) bglP, 27) cccA, 28) dctP, 30) glpF, 33) phoP, 45) and acuA. 19) The binding of the protein complex to a cre site located well downstream of the transcription initiation base is considered to block transcription elongation, as for most of the other operons listed in Table 1.…”

“…43) The yxkF-msmX operon probably involved in the transport of unknown sugars has been found to be under CcpA-mediated CCR. 25,49) Besides, the amyE gene encoding the extracellular -amylase hydrolyzing starch, 3,5) and the levDEFG-sacC operon encoding a fructose-specific phosphotransferase system and the extracellular levanase hydrolyzing fructose polymers and sucrose, 59,104) are also known to be subject to CcpA-mediated CCR. In addition, some members (lcfA-fadR-fadB-etfAB, fadNAE, and lcfB) of the FadR (formerly YsiA) regulon involved in fatty acid degradation 44,105) are under CcpA-dependent CCR (H. Matsuoka, and Y. Fujita, unpublished observation).…”

Regulation of amylase gene expression in diabetic mice is mediated by a cis-acting upstream element close to the pancreas-specific enhancer.

“…For example, transcription of bacterial amylase is regulated by the catabolite repression mechanism (Nicholson et al 1987), and amylase can be repressed in Drosophila by feeding a diet high in glucose (Benkel and Hickey 1986). Because the diabetic state in mammals is characterized by elevated concentrations of circulating glucose, it may be analogous physiologically to conditions of glucose abundance in lower organisms.…”