Disease relevance of pyrB

• RNA polymerase involvement in the regulation of expression of Salmonella typhimurium pyr genes. Isolation and characterization of a fluorouracil-resistant mutant with high, constitutive expression of the pyrB and pyrE genes due to a mutation in rpoBC [1].
• Carbamyl aspartate toxicity was shown to be useful as a phenotypic trait for classifying pyrimidine auxotrophs and may also be useful for positive selection of pyrA or pyrB mutants [2].
• Genes encoding Escherichia coli aspartate transcarbamoylase: the pyrB-pyrI operon [3].

High impact information on pyrB

• Another deletion, pyrB740, shares a similar terminus at one end within pyrB, but the promoter region is removed [3].
• Evidence for this single transcriptional unit was obtained by a study of various deletion mutations and from the DNA sequence of the intercistronic region between pyrB and pyrI [3].
• The introduction of either a pyrA or pyrB mutation into a pyrC strain eliminated the observed growth inhibition [2].
• It should accumulate to high levels in pyrC or pyrD mutants when expression of the pyrA and pyrB genes is elevated [2].
• Introduction of leaky mutation argI2002 resulted in a more extreme arginine requirement and accentuated suppression by pyrB mutations [4].

Biological context of pyrB

• This technique was also used to make larger chromosomal duplications between Mud 1-8 insertions in the thr and leu biosynthetic operons and between Mud insertions in the thr and pyrB operons [5].
• Together with the phenotype of the rpoBC mutant, these results indicate that expression of pyrB and pyrE is regulated by the mRNA chain growth rate, which is controlled by the cellular UTP pool [6].
• We investigated the transcription kinetics of RNA polymerase from an rpoBC mutant of Salmonella typhimurium which showed highly elevated, constitutive expression of the pyrB and pyrE genes as well as an increased cellular pool of UTP [6].
• The mutation maps at unit 99 of the S. typhimurium chromosome between pyrB and deoC [7].

Other interactions of pyrB

• The relative orientation of these markers is pepA argI pyrB [8].
• The direction of transcription of pyrB was determined to be counterclockwise on the S. typhimurium linkage map and argI was shown to be located clockwise of pyrB [9].

Analytical, diagnostic and therapeutic context of pyrB

• Molecular cloning and subsequent DNA analysis demonstrated that the pyrB and pyrI genes are contiguous with pyrI as the distal gene in the operon [3].

References