Synthesis of FinP RNA by plasmids F and pSLT is regulated by DNA adenine methylation

DNA adenine methylase mutants of Salmonella typhimurium contain reduced amo unts of FinP, an antisense RNA encoded by the virulence plasmid pSLT. Lower ed FinP levels are detected in both Dam(-) FinO(+) and Dam(-) FinO(-) backg rounds, suggesting that Dam methylation regulates FinP production rather th an FinP half-life. Reduced amounts of F-encoded FinP RNA are likewise found in Dam(-) mutants of Escherichia coli. A consequence of FinP RNA scarcity in the absence of DNA adenine methylation is that Dam(-) mutants of both S. typhimurium and E. coli show elevated levels of F plasmid transfer. Inhibi tion of F fertility by the S. typhimurium virulence plasmid is also impaire d in a Dam(-) background.