ClpC and MecA, components of a proteolytic machine, prevent Spo0A-P-dependent transcription without degradation

5 years ago

ClpC and MecA, components of a proteolytic machine, prevent Spo0A-P-dependent transcription without degradation

David Dubnau, Valerie J. Carabetta, Andrew W. Tanner

In Bacillus subtilis, a proteolytic machine composed of MecA, ClpC and ClpP degrades the transcription factor ComK, controlling its accumulation during growth. MecA also inhibits sporulation and biofilm formation by down-regulating spoIIG and sinI, genes that are dependent for their transcription on the phosphorylated protein Spo0A-P. Additionally, MecA has been shown to interact in vitro with Spo0A. Although the inhibitory effect on transcription requires MecA's binding partner ClpC, inhibition is not accompanied by the degradation of Spo0A, pointing to a previously unsuspected regulatory mechanism involving these proteins. Here, we further investigate the MecA and ClpC effects on Spo0A-P-dependent transcription. We show that MecA inhibits the transcription of several Spo0A-P activated genes, but fails to de-repress several Spo0A-P repressed promoters. This demonstrates that MecA and ClpC do not act by preventing the binding of Spo0A-P to its target promoters. Consistent with this, MecA by itself has no effect in vitro on the transcription from PspoIIG while the addition of both MecA and ClpC has a strong inhibitory effect. A complex of MecA and ClpC likely binds to Spo0A-P on its target promoters, preventing the activation of transcription. Thus, components of a degradative machine have been harnessed to directly repress transcription. This article is protected by copyright. All rights reserved. MecA and ClpC inhibit the transcription of genes that are activated by Spo0A-P but do not de-repress those that are repressed. This suggests that MecA and ClpC do not prevent Spo0A-P binding to its target promoters. Instead, in vitro and in vivo data support a model in which these proteins assemble with Spo0A-P on the DNA template, perhaps preventing RNA polymerase from binding.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/mmi.13928