Brahma is required for cell cycle arrest and late muscle gene expression during skeletal myogenesis

Although the two catalytic subunits of the SWI/SNF chromatin-remodeling complex—Brahma (Brm) and Brg1—are almost invariably co-expressed, their mutually exclusive incorporation into distinct SWI/SNF complexes predicts that Brg1- and Brm-based SWI/SNF complexes execute specific functions. Here, we show that Brg1 and Brm have distinct functions at discrete stages of muscle differentiation. While Brg1 is required for the activation of muscle gene transcription at early stages of differentiation, Brm is required for Ccnd1 repression and cell cycle arrest prior to the activation of muscle genes. Ccnd1 knockdown rescues the ability to exit the cell cycle in Brm-deficient myoblasts, but does not recover terminal differentiation, revealing a previously unrecognized role of Brm in the activation of late muscle gene expression independent from the control of cell cycle. Consistently, Brm null mice displayed impaired muscle regeneration after injury, with aberrant proliferation of satellite cells and delayed formation of new myofibers. These data reveal stage-specific roles of Brm during skeletal myogenesis, via formation of repressive and activatory SWI/SNF complexes

TFIIB recognition elements control the TFIIA-NC2 axis in transcriptional regulation

TFIIB recognizes DNA sequence-specific motifs that can flank the TATA elements of the promoters of protein-encoding genes. The TFIIB recognition elements (BREu and BREd) can have positive or negative effects on transcription in a promoter context-dependent manner. Here we show that the BREs direct the selective recruitment of TFIIA and NC2 to the promoter. We find that TFIIA preferentially associates with BRE-containing promoters while NC2 is recruited to promoters that lack consensus BREs. The functional relevance of the BRE-dependent recruitment of TFIIA and NC2 was determined by small interfering RNA-mediated knockdown of TFIIA and NC2, both of which elicited BRE-dependent effects on transcription. Our results confirm the established functional reciprocity of TFIIA and NC2. However, our findings show that TFIIA assembly at BRE-containing promoters results in reduced transcriptional activity, while NC2 acts as a positive factor at promoters that lack functional BREs. Taken together, our results provide a basis for the selective recruitment of TFIIA and NC2 to the promoter and give new insights into the functional relationship between core promoter elements and general transcription factor activity

Déterminants de la consommation des antibiotiques et de la résistance de Staphylococcus Aureus à la méticiline dans les établissements de santé

En France, les établissements de santé ont été incités à surveiller leurs consommations des antibiotiques et leurs résistances bactériennes. Nos objectifs étaient d'étudier les déterminants de la consommation des antibiotiques et de la résistance de Staphylococcus aureus à la méticilline (SARM) dans 99 établissements de santé de l'interrégion Sud-Ouest afin de préciser les modalités d'interprétation des données et d'étudier les liens existants avec les politiques mises en place. Au delà de la typologie habituellement utilisée d'autres critères d'ajustement doivent être pris en compte pour une comparaison inter établissements. Les politiques de bon usage des antibiotiques et de lutte contre les infections nosocomiales étaient associées à une plus forte consommation d'antibiotiques et à une incidence plus élevée de SARM. L'incidence de SARM était corrélée à la consommation des fluoroquinolones mais la méthode ne permettait pas de préjuger d'une relation de causalité. L'analyse des données agrégées peut aider à l'interprétation des variations observées pour une comparaison des indicateurs dans les établissements de santé.Due to the high resistance rate and excessive use of antibiotics, French government has recommended that hospitals should monitor antibiotics consumption and incidence of methicillin-resistant Staphylococcus aureus (MRSA). Our aim was to determine factors that correlate with antibiotics use and Staphylococcus aureus resistance among 99 hospitals in south western France and to study relationship between these two indicators and policies developed by hospitals. Hospital type and hospitals areas stratification seems to be not enough homogenous to make valid comparisons. Number of beds could be used to explain difference when indicator of case mix is not available. Antibiotics policies and infection control program were associated with high consumption and high resistance rates. Fluoroquinolone use correlated with MRSA incidence but the relationships between antibiotic use and MRSA are complex and aggregated data do not prove causality link. However, such aggregated data may be helpful for comparison purpose.BORDEAUX2-BU Santé (330632101) / SudocPARIS-BIUP (751062107) / SudocSudocFranceF

TBP/TFIID-dependent activation of myoD target genes in skeletal muscle cells

Change in the identity of the components of the transcription pre-initiation complex is proposed to control cell type-specific gene expression. Replacement of the canonical TFIID-TBP complex with TRF3/TBP2 was reported to be required for activation of muscle-gene expression. The lack of a developmental phenotype in TBP2 null mice prompted further analysis to determine whether TBP2 deficiency can compromise adult myogenesis. We show here that TBP2 null mice have an intact regeneration potential upon injury and that TBP2 is not expressed in established C2C12 muscle cell or in primary mouse MuSCs. While TFIID subunits and TBP are downregulated during myoblast differentiation, reduced amounts of these proteins form a complex that is detectable on promoters of muscle genes and is essential for their expression. This evidence demonstrates that TBP2 does not replace TBP during muscle differentiation, as previously proposed, with limiting amounts of TFIID-TBP being required to promote muscle-specific gene expression

DEFOG: A Practical Scheme for Deciphering Families of Genes

We developed a novel efficient scheme, DEFOG (for "deciphering families of genes"), for determining sequences of numerous genes from a family of interest. The scheme provides a powerful means to obtain a gene family composition in species for which high-throughput genomic sequencing data are not available. DEFOG uses two key procedures. The first is a novel algorithm for designing highly degenerate primers based on a set of known genes from the family of interest. These primers are used in PCR reactions to amplify the members of the gene family. The second combines oligofingerprinting of the cloned PCR products with clustering of the clones based on their fingerprints. By selecting members from each cluster, a low-redundancy clone subset is chosen for sequencing. We applied the scheme to the human olfactory receptor (OR) genes. OR genes constitute the largest gene superfamily in the human genome, as well as in the genomes of other vertebrate species. DEFOG almost tripled the size of the initial repertoire of human ORs in a single experiment, and only 7% of the PCR clones had to be sequenced. Extremely high degeneracies, reaching over a billion combinations of distinct PCR primer pairs, proved to be very effective and yielded only 0.4% nonspecific products