title: Adaptor protein MecA is a negative regulator of the expression of late competence genes in Streptococcus thermophilus.
abstract: In Streptococcus thermophilus, the ComRS regulatory system governs the transcriptional level of comX expression and, hence, controls the early stage of competence development. The present work focuses on the posttranslational control of the activity of the sigma factor ComX and, therefore, on the late stage of competence regulation. In silico analysis performed on the S. thermophilus genome revealed the presence of a homolog of mecA (mecA(St)), which codes for the adaptor protein that is involved in ComK degradation by ClpCP in Bacillus subtilis. Using reporter strains and microarray experiments, we showed that MecA(St) represses late competence genes without affecting the early competence stage under conditions that are not permissive for competence development. In addition, this repression mechanism was found not only to act downstream of comX expression but also to be fully dependent on the presence of a functional comX gene. This negative control was similarly released in strains deleted for clpC, mecA, and clpC-mecA. Under artificial conditions of comX expression, we next showed that the abundance of ComX is higher in the absence of MecA or ClpC. Finally, results of bacterial two-hybrid assays strongly suggested that MecA interacts with both ComX and ClpC. Based on these results, we proposed that ClpC and MecA act together in the same regulatory circuit to control the abundance of ComX in S. thermophilus.
authors.affiliation: Biochimie et Génétique Moléculaire Bactérienne, Institut des Sciences de la Vie, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
authors.forename: Céline
authors.initials: C
authors.lastname: Boutry
authors.forename: Astrid
authors.initials: A
authors.lastname: Wahl
authors.forename: Brigitte
authors.initials: B
authors.lastname: Delplace
authors.forename: André
authors.initials: A
authors.lastname: Clippe
authors.forename: Laetitia
authors.initials: L
authors.lastname: Fontaine
authors.forename: Pascal
authors.initials: P
authors.lastname: Hols
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D048249:Streptococcus thermophilus / Q000235:genetics* / Q000378:metabolism*; D014169:Transformation, Bacterial
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins