m-2 UV-irradiation indicated that orfs90/91, orf43 and the previously documented UV-inducible orf4 (jef, Figure 1) [14] were up-regulated after exposure to UV irradiation. Analysis indicated that orf4 PF-3084014 (jef) specific mRNA levels were up-regulated 0.78 fold, orf43, 0.513 fold and orfs9091, 0.339 fold. In contrast other ICE R391 genes not involved in cell sensitisation [8] were not up-regulated post exposure: aph (encoding Kanamycin resistance) was

down-regulated 0.23 fold post-exposure while orf31 (encoding a putative Lon protease) was also down-regulated 0.19 fold post-exposure. Analysis of the up-regulated genes in mutant backgrounds indicated that in a Δorfs90/91 (∆26) background, orf43 up-regulation was abolished (Figure 2) while analysis of orfs90/91 transcription in a Δorf43 (∆14) background did not prevent orfs90/91 specific mRNA up-regulation following UV irradiation (orfs90/91 up-regulated selleckchem 0.61 fold in AB1157 R391 ∆14). This indicated a dependency on orfs90/91 for orf43 up-regulation but not vice versa. Further analysis of orf43 transcription in a Δorfs40/41 mutant (Δ11) [8] demonstrated that deletion of these genes, upstream of orf43, did not prevent the UV-induced up-regulation of orf43 mRNA, suggesting that inducible orf43 transcription was stimulated through a region directly in front of the orf43 gene (Figure 2) and that this region should

be investigated further. This observation is supported by previous deletion analysis where orfs40/41 (Δ11) and ∆orf42 (∆13) were deleted but retained the UV-inducible sensitising phenotype [8]. Analysis of the up-regulated orfs90/91 and orf43 mRNA decay rate post-exposure (Figure 3) revealed that orfs90/91 mRNA levels were maximally up-regulated directly after exposure and selleck decayed rapidly with a return to basal levels within 5 minutes post-exposure. However orf43 mRNA levels were maximally up-regulated 7 minutes post-exposure and up-regulated levels were sustained for a longer period of time, minimally over 30 minutes (Figure 3). The observation of the rapid increase

and decay of orfs90/91 specific mRNA levels followed by a slower and longer sustained increase in orf43 specific mRNA Buspirone HCl levels supports the hypothesis that UV irradiation acts as an inducing agent for orfs90/91, which subsequently up-regulates the transcription of orf43 possibly from a site preceding the gene. Figure 2 Increase in orf43 mRNA levels after exposure to 40 J.m -2 UV irradiation. Backgrounds analysed were AB1157 R391, AB1157 R391 ∆26 (∆orfs90/91) and AB1157 R391 ∆11 (∆orfs40/41). All results were normalised using the endogenous constitutively expressed proC gene. Average values were calculated from a minimum of 9 replicates for each strain analysed. Figure 3 Decay of AB1157 R391 orfs90/91 and orf43 mRNA levels after exposure to 40 J.m -2 UV irradiation. All results were normalised using the endogenous constitutively expressed proC gene. Standard deviation is denoted by markers above and below all data points.