SEQUENCE AND STRUCTURE OF CMP, THE REPLICATION ENHANCER OF THE STAPHYLOCOCCUS-AUREUS PLASMID-PT181

The Staphylococcus aureus plasmid pT181 possesses a DNA replication en hancer element, called cmp, that is required in cis for optimal utiliz ation of the initiator protein by the origin of replication. The minim al nucleotide sequence required for cmp activity was defined by testin g progressively smaller DNA fragments for their ability to restore cmp activity in a plasmid mutant deleted for emp. These experiments indic ate that cmp is a sequence of 100 base pairs (bp) characterized by a l oosely repeated sequence motif and phased oligo(dT) tracts. Intrinsic DNA bending at cmp was detected by a circular permutation assay of the locus using polyacrylamide-gel electrophoresis and by computer modeli ng. The cmp element was found to contain two loci of intrinsically ben t DNA that confer an overall bent conformation to this replication enh ancer.