FIG 7.

Model of pBS32-mediated cell death. MMC-mediated DNA damage causes LexA autoproteolysis and derepression of sigN expression. SigN is a sigma factor that directs RNA polymerase to increase its own expression (creating positive feedback) and the expression of a regulon of genes on pBS32. Activation of genes within the SigN regulon results in cell death. pBS32 is represented as a circle. Arrows within the circle indicate reading frames. The location of SigN-dependent promoters is indicated by red arrowheads. Reading frames and gene names that are expressed by SigN are indicated in red. T bars indicate inhibition, and arrows indicate activation. In black are the locations of specific promoters mentioned in the text.