TRANSCRIPTIONAL ANALYSIS OF ROLLING CIRCLE REPLICATING PLASMID PVT736-1 - EVIDENCE FOR REPLICATION CONTROL BY ANTISENSE RNA

Several plasmids have been described in Actinobacillus actinomycetemco mitans, a gram-negative coccobacillus. Recently, the nucleotide sequen ce of pVT736-1, a cryptic plasmid of A. actinomycetemcomitans VT736, w as determined. This plasmid possesses all the features necessary for r olling circle replication. The present study involved a transcriptiona l analysis of pVT736-1. Results of Northern (RNA) blot analyses and pr imer extension studies indicated that the two open reading frames iden tified in pVT736-1 are each preceded by at least one promoter. Express ion of these promoters varied with growth phase. In addition, an antis ense RNA (Cop RNA) appeared to control the synthesis of the putative r eplication protein. To our knowledge, this is the first rolling circle replicating plasmid isolated from a gram-negative organism that has b een subjected to such detailed analysis.