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Title: TRANSCRIPTIONAL REGULATION OF THE OSPAB AND OSPC PROMOTERS IN BORRELIA BURGDORFERI

Author
item Alverson, Janet
item SOHASKEY, CHARLES - V.A.MED.CTR, CALIFORNIA
item SAMUELS, D. SCOTT - UNIV. OF MONTANA

Submitted to: Molecular Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/3/2003
Publication Date: 3/3/2003
Citation: ALVERSON, J., SOHASKEY, C.D., SAMUELS, D. TRANSCRIPTIONAL REGULATION OF THE OSPAB AND OSPC PROMOTERS IN BORRELIA BURGDORFERI. MOLECULAR MICROBIOLOGY. 2003. v. 48(6). p.1665-1677.

Interpretive Summary: Lyme disease is a multisystem disorder of humans and animals caused by the bacterium Borrelia burgdorferi. The outer surface proteins, OspA and OspC, are differentially expression in the vector tick and the mammalian host. DNA supercoiling is a state in which double-stranded DNA molecules are further twisted. We examined the regulation of ospA and ospC promoter activity by DNA supercoiling using a reporter expression system in both Escherichia coli and B. burgdorferi. We found that both ospA and ospC promoters responded to changes in DNA supercoiling in B. burgdorferi, but only the ospC promoter responded in E. coli. Our data suggests the presence of a trans-acting factor in B. burgdorferi that is not present in E. coli for the ospA promoter. This research is of benefit to the scientific and medical communities investigating mechanisms of bacterial gene regulation and the pathogenesis of this important bacterial disease.

Technical Abstract: The regulation of ospA and ospC promoter activity by DNA supercoiling in Borrelia burgdorferi was examined using a chloramphenicol acetyltransferase (CAT) gene as a reporter expression system in both Escherichia coli and B. burgdorferi. DNA supercoiling was relaxed by shifting B. burgdorferi to a higher temperature or by adding coumermycin A1, an antibiotic that targets DNA gyrase and inhibits DNA supercoiling. The activities of the ospA and ospC promoters were regulated by perturbing DNA supercoiling in B. burgdorferi, but only the ospC promoter responded to DNA relaxation in E. coli. Less negatively supercoiled DNA resulted in a decrease in ospA promoter activity and an increase in ospC promoter activity in B. burgdorferi, and an increase in ospC promoter activity in E. coli. The ospA and ospC mRNA transcripts were also examined by Northern blot for B. burgdorferi cultures grown at 23?C or 35?C, and with various amounts of coumermycin A1 added. The ospA promoter showed decreased activity at the higher temperature and with the addition of coumermycin A1, while the ospC promoter had an increased activity under these conditions. We also examined this system in a genetic mutant of the gyrB gene and showed that ospC activity was increased in cells with a defective gyrase. Our data suggests the presence of a trans-acting factor in B. burgdorferi that is not present in E. coli for the ospA promoter.