MrpC, a CRP/Fnr homolog, functions as a negative autoregulator during the Myxococcus xanthus Myxococcus xanthus multicellular developmental program

摘要

Summary MrpC, a member of the CRP/Fnr superfamily of transcriptional regulators, plays a key role in coordination of the multicellular developmental program inMyxococcus xanthus . Previous reports suggest MrpC is subject to complex regulation including activation by an unusual LonDdependent proteolytic processing event that removes its unique Nterminal peptide, producing the isoform MrpC2. MrpC2 is proposed to positively autoregulate and regulate transcription of hundreds of genes necessary for both the aggregation and sporulation phases of the developmental program. We demonstrate here thatmrpC expression bifurcates corresponding to different cell populations within the developmental program. During our analysis of regulatory events controlling this process, we demonstrate that MrpC2 is not an active isoform; rather, the Nterminal peptide is instead essential for MrpC functionin vivo . We also demonstrate that MrpC is instead a negative autoregulator and represses its own expression by specifically competing with its enhancer binding protein, MrpB. These results provide an additional rare example of CRP/EBP coordinated regulation, and significantly revise the model for control of the central developmental transcriptional activator of theM. xanthus developmental program.