Biomedical subjects

Mark Albano

Publications and source records attributed to Mark Albano.

3 recordsLinked to original sources

PubMed2005

The Rok protein of Bacillus subtilis represses genes for cell surface and extracellular functions.

Rok is a repressor of the transcriptional activator ComK and is therefore an important regulator of competence in Bacillus subtilis (T. T. Hoa, P. Tortosa, M. Albano, and D. Dubnau, Mol. Microbiol. 43:15-26, 2002). To address the wider role of Rok in the physiology of B. subtilis, we have used a combination of transcriptional profiling, gel shift experiments, and the analysis of lacZ fusions. We demonstrate that Rok is a repressor of a family of genes that specify membrane-localized and secreted proteins, including a number of genes that encode products with antibiotic activity. We present evidence for the recent introduction of rok into the B. subtilis-Bacillus licheniformis-Bacilllus amyloliquefaciens group by horizontal transmission.

Bacillus subtilis↗

PubMed2002

Rok (YkuW) regulates genetic competence in Bacillus subtilis by directly repressing comK.

The Rok (YkuW) protein acts as a negative regulator of comK, which encodes the competence transcription factor of Bacillus subtilis. In the absence of Rok, ComK is overproduced, and when excess Rok is present comK transcription is inhibited. Rok acts transcriptionally to repress comK expression but does not affect ComK stability, which is controlled by the MecA switch. Gel-shift assays show that Rok binds directly to a DNA fragment that contains the comK promoter. SinR and AbrB act negatively on rok transcription, and the inactivation of rok bypasses the positive requirements for sinR and abrB for the expression of comK. Therefore, the dependence of comK expression on SinR and AbrB may be a result of their repression of rok transcription. It has also been shown in vivo that Rok and ComK can indivi-dually repress rok transcription, and that Rok and ComK bind to the rok promoter in vitro. These interactions establish feedback loops, and the roles of these circuits are discussed.

Bacillus subtilis↗

PubMed2002

Microarray analysis of the Bacillus subtilis K-state: genome-wide expression changes dependent on ComK.

In Bacillus subtilis, the competence transcription factor ComK activates its own transcription as well as the transcription of genes that encode DNA transport proteins. ComK is expressed in about 10% of the cells in a culture grown to competence. Using DNA microarrays representing approximately 95% of the protein-coding open reading frames in B. subtilis, we compared the expression profiles of wild-type and comK strains, as well as of a mecA mutant (which produces active ComK in all the cells of the population) and a comK mecA double mutant. In these comparisons, we identified at least 165 genes that are upregulated by ComK and relatively few that are downregulated. The use of reporter fusions has confirmed these results for several genes. Many of the ComK-regulated genes are organized in clusters or operons, and 23 of these clusters are preceded by apparent ComK-box promoter motifs. In addition to those required for DNA uptake, other genes that are upregulated in the presence of ComK are probably involved in DNA repair and in the uptake and utilization of nutritional sources. From this and previous work, we conclude that the ComK regulon defines a growth-arrested state, distinct from sporulation, of which competence for genetic transformation is but one notable feature. We suggest that this is a unique adaptation to stress and that it be termed the 'K-state'.

Bacillus subtilis↗