GO profiling demonstrated a prominent differential effect related to rRNA processing and ribosomal biogenesis, which were repressed Necrostatin-1 by PAF26 but induced by melittin. A high number of genes from these annotations showed this marked differential response with extremely significant p-values (Additional File 4), including the group of seven genes induced by melittin and repressed by PAF26 (Figure 2), and was also confirmed by quantitative RT-PCR in

selected genes (Figure 3A, CGR1 and NOP16). The repression this website behavior is shared in the response to other AMP, antimicrobial compounds and additional stress conditions [35, 38, 61]. mRNAs from ribosomal proteins and rRNA processing enzymes are predicted to destabilize under stress conditions [71]. It is assumed PRI-724 in vivo that shutdown of ribosome biogenesis and thus protein translation will free cell resources to cope with a hostile environment.

However, our study opens additional questions as to the significance of the induction (rather than repression) of this response in the case of melittin, or of the increased resistance to PAF26 in some of the corresponding deletion strains such as that of the nucleolar protein NOP16 (Figure 5A). The gene BTN2 has been reported to modulate arginine uptake through down-regulation of the CAN1p arginine permease [59]. Our study shows that BTN2 was one of the most repressed gene by both peptides (Additional File 3), suggesting that the cell is sensing the high arginine levels caused by peptide internalization and mounts an active response to deal with it. GO profiling indicated the specific involvement of the “”nonprotein amino acid metabolic process”" PJ34 HCl in the response to PAF26, including genes from the biosynthesis or arginine, metabolism

of amino groups and urea cycle (ARG1, ARG3, ARG5,6 and ARG7), which were induced by PAF26 but not by melittin. ARG1 was the gene with the highest PAF26-specific induction identified in our macroarray study, and such strong expression change was confirmed through qRT-PCR analysis (Figure 3). ARG1 codes for the argininosuccinate synthase and is known to be transcriptionally repressed in the presence of arginine. Induction of these genes is indicative of attempt of metabolization of the high concentration of amino groups of cationic AMP such as PAF26. In fact, their induction could lead to accumulation of derived metabolites in the cell. Although the question of ammonium toxicity in yeast is still controversial [72], we speculate that this could be the case given the higher resistance to PAF26 of the deletion mutants assayed. In any case the high resistance to PAF26 of a number of ARG gene deletants confirms the involvement of these pathways in the peptide killing mechanism (Figure 5B). Importantly, susceptibility to PAF26 did not correlate with peptide interaction/internalization into cells in Δarg1 (Figure 7).