Bielińska A, Hulanicka D
J Gen Microbiol. 1986 Sep;132(9):2571-6. doi: 10.1099/00221287-132-9-2571.
cysB, the regulatory gene of the cysteine regulon, is autoregulated. Inhibitors of both gyrase subunits, nalidixic acid and novobiocin, affect the expression of cysB, as monitored by beta-galactosidase activity in cysB::lac fusion strains. In gyrA mutants that are resistant to nalidixic acid, this drug does not affect cysB expression. The amount of mRNA transcribed from the cysB promoter isolated from cultures grown in the presence of gyrase inhibitors was significantly lower than that from the control culture without inhibitors. Urea also decreased cysB expression. These results suggest that DNA topology could play a role in cysB expression.
半胱氨酸调节子的调节基因cysB是自我调节的。通过cysB::lac融合菌株中的β-半乳糖苷酶活性监测发现，回旋酶两个亚基的抑制剂萘啶酸和新生霉素都会影响cysB的表达。在对萘啶酸耐药的gyrA突变体中，这种药物不影响cysB的表达。从在回旋酶抑制剂存在下培养的培养物中分离出的cysB启动子转录的mRNA量显著低于没有抑制剂的对照培养物。尿素也会降低cysB的表达。这些结果表明DNA拓扑结构可能在cysB的表达中起作用。
