Biomedical subjects

Etienne Dervyn

Publications and source records attributed to Etienne Dervyn.

6 recordsLinked to original sources

PubMed2004

The bacterial condensin/cohesin-like protein complex acts in DNA repair and regulation of gene expression.

Structural maintenance of chromosome (SMC) and the SMC-interacting kleisin protein families have key functions in the chromosome organization of most organisms. Here, we report that the Bacillus subtilis kleisin, ScpA, can form a ternary complex with the SMC and ScpB proteins in a yeast tri-hybrid assay, supporting the notion of a bacterial cohesin/condensin-like complex. Furthermore, ScpA interacts in two-hybrid assays with the AddAB complex, essential for recombinational repair, with DegS, a two-component sensor kinase, as well as with other potential transcription regulators. Point mutations in scpA allowing growth under conditions not permissive for the spcA null and not affecting chromosome condensation were isolated. Among these mutations, some affected DNA repair and gene regulation, thus separating ScpA functions in these two pathways from its functions in chromosome condensation and segregation. Some separation-of-function mutations in scpA caused a deficiency in the repair of mitomycin C DNA lesions that was suppressed by increasing the intracellular dosage of the interacting AddAB complex. Another mutation in scpA deregulated the expression of genes encoding degradative enzymes that are known to be controlled by the interacting DegS kinase. We propose that the SMC-ScpA-ScpB complex could: (i) recruit the AddAB helicase/nuclease to act in post-replicative repair; and (ii) form a complex with the DegS sensor kinase that inhibits its kinase activity. Moreover, our results indicate that the role of cohesin and condensin complexes in DNA repair and gene regulation is evolutionary conserved.

Bacillus subtilis↗

PubMed2004

Genes involved in formation of structured multicellular communities by Bacillus subtilis.

The spore-forming bacterium Bacillus subtilis is capable of assembling multicellular communities (biofilms) that display a high degree of spatiotemporal organization. Wild strains that have not undergone domestication in the laboratory produce particularly robust biofilms with complex architectural features, such as fruiting-body-like aerial projections whose tips serve as preferential sites for sporulation. To discover genes involved in this multicellular behavior and to do so on a genome-wide basis, we took advantage of a large collection of mutants which have disruptions of most of the uncharacterized genes in the B. subtilis genome. This collection, which was generated with a laboratory strain, was screened for mutants that were impaired in biofilm formation. This subset of mutated genes was then introduced into the wild strain NCIB 3610 to study their effects on biofilm formation in liquid and solid media. In this way we identified six genes that are involved in the development of multicellular communities. These are yhxB (encoding a putative phosphohexomutase that may mediate exopolysaccharide synthesis), sipW (encoding a signal peptidase), ecsB (encoding an ABC transporter subunit), yqeK (encoding a putative phosphatase), ylbF (encoding a regulatory protein), and ymcA (a gene of unknown function). Further analysis revealed that these six genes play different roles in B. subtilis community development.

Bacillus subtilis↗

PubMed2002

An expanded view of bacterial DNA replication.

A protein-interaction network centered on the replication machinery of Bacillus subtilis was generated by genome-wide two-hybrid screens and systematic specificity assays. The network consists of 91 specific interactions linking 69 proteins. Over one fourth of the interactions take place between homologues of proteins known to interact in other organisms, indicating the high biological significance of the other interactions we report. These interactions provide insights on the relations of DNA replication with recombination and repair, membrane-bound protein complexes, and signaling pathways. They also lead to the biological role of unknown proteins, as illustrated for the highly conserved YabA, which is shown here to act in initiation control. Thus, our interaction map provides a valuable tool for the discovery of aspects of bacterial DNA replication.

Bacillus subtilis↗

PubMed2002

Discovery of two novel families of proteins that are proposed to interact with prokaryotic SMC proteins, and characterization of the Bacillus subtilis family members ScpA and ScpB.

Structural maintenance of chromosomes (SMC) proteins are present in all eukaryotes and in many prokaryotes. Eukaryotic SMC proteins form complexes with various non-SMC subunits, which affect their function, whereas the prokaryotic homologues had no known non-SMC partners and were thought to act as simple homodimers. Here we describe two novel families of proteins, widespread in archaea and (Gram-positive) bacteria, which we denote 'segregation and condensation proteins' (Scps). ScpA genes are localized next to smc genes in nearly all SMC- containing archaea, suggesting that they belong to the same operon and are thus involved in a common process in the cell. The function of ScpA was studied in Bacillus subtilis, which also harbours a well characterized smc gene. Here we show that scpA mutants display characteristic phenotypes nearly identical to those of smc mutants, including temperature- sensitive growth, production of anucleate cells, formation of aberrant nucleoids, and chromosome splitting by the so-called guillotine effect. Thus, both SMC and ScpA are required for chromosome segregation and condensation. Interestingly, mutants of another B. subtilis gene, scpB, which is localized downstream from scpA, display the same phenotypes, which indicate that ScpB is also involved in these functions. ScpB is generally present in species that also encode ScpA. The physical interaction of ScpA and SMC was proven (i) by the use of the yeast two-hybrid system and (ii) by the isolation of a complex containing both proteins from cell extracts of B. subtilis. By extension, we speculate that interaction of orthologues of the two proteins is important for chromosome segregation in many archaea and bacteria, and propose that SMC proteins generally have non-SMC protein partners that affect their function not only in eukaryotes but also in prokaryotes.

Amino Acid Sequence↗

PubMed1998

A vector for systematic gene inactivation in Bacillus subtilis.

To study the functions of the uncharacterized open reading frames identified in the Bacillus subtilis genome, several vectors were constructed to perform insertional mutagenesis in the chromosome. All the pMUTIN plasmids carry a lacZ reporter gene and an inducible Pspac promoter, which is tightly regulated and can be induced about 1000-fold. The integration of a pMUTIN vector into the target gene has three consequences: (1) the target gene is inactivated; (2) lacZ becomes transcriptionally fused to the gene, allowing its expression pattern to be monitored; (3) the Pspac promoter controls the transcription of downstream genes in an IPTG-dependent fashion. This last feature is important because B. subtilis genes are often organized in operons. The potential polar effects generated by the integration of the vectors can be alleviated by addition of IPTG. Also, conditional mutants of essential genes can be obtained by integrating pMUTIN vectors upstream of the target gene. The vectors are currently being used for systematic inactivation of genes without known function within the B. subtilis European consortium. pMUTIN characteristics and the inactivation of eight genes in the resA-serA region of the chromosome are presented.

Bacillus subtilis↗

PubMed1997

Spo0A represses transcription of the cry toxin genes in Bacillus thuringiensis.

The DNA regions upstream from the genes encoding polypeptides of Bacillus thuringiensis subsp. israelensis larvicidal crystals (cry4A, cry4B, cry11A) contain sequences with similarities to the spo0A box of Bacillus subtilis (or '0A' box) and the promoter recognized by the sigma H-associated RNA polymerase of B. subtilis. Expression of cry-lacZ transcriptional fusions was analysed in various B. thuringiensis genetic backgrounds. The early transcription of the toxin genes was not sporulation-dependent, whereas the late-stage expression at t4-6 was sigma E-dependent. Primer extension analysis confirmed that the cry4- and cry11-type toxin genes were weakly transcribed during the transition phase; expression analysis of a cry11A'-lacZ transcriptional fusion in B. subtilis sporulation mutants confirmed the involvement of the sigma H-RNA polymerase. Primer extension analysis showed that in B. thuringiensis subsp. israelensis, the cry4A and cry11A gene transcription observed at the end of the growth stage was turned off at the beginning of the sporulation phase. The DNA region located upstream from the cry11A gene promoter including the putative '0A' box was deleted. This led to a derepression of the expression of the cry11A operon. These results suggest that the cry4A, cry4B and cry11A toxin genes of B. thuringiensis subsp. Israelensis are transcribed during the transition phase by the RNA polymerase associated with the sigma H factor and are subject to Spo0A repression.

Bacillus subtilis↗