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The smallest product of the Duchenne muscular dystrophy gene, dystrophin (Dp)71, is ubiquitously expressed in nonmuscle tissues. We previously showed that Dp71 expression in hepatic cells is modulated in part by stimulating factor 1 (Sp1), stimulating protein 3 (Sp3), and yin yang 1 (YY1) transcription factors, and that the polyaromatic hydrocarbon, β-naphthoflavone (β‑NF), downregulates Dp71 expression. The aim of the present study was to determine whether β‑NF represses Dp71 expression by altering mRNA stability or its promoter activity. Reverse transcription‑quantitative polymerase chain reaction was used to measure half‑life mRNA levels in β‑NF‑treated cells exposed to actinomycin D, an inhibitor of transcription, for 0, 4, 8, 12 and 16 h. Transient transfections with a plasmid carrying the Dp71 basal promoter fused to luciferase reporter gene were carried out in control and β‑NF‑treated cells. Electrophoretic mobility shift assays (EMSAs) were performed with labeled probes, corresponding to Dp71 promoter sequences, and nuclear extracts of control and β‑NF‑treated cells. To the best of our knowledge, the results demonstrated for the first time that this negative regulation takes place at the promoter level rather than the mRNA stability level. Interestingly, using EMSAs, β‑NF reduced binding of YY1, Sp1, and Sp3 to the Dp71 promoter. It also suggests that β‑NF may modulate the expression of other genes regulated by these transcription factors. In conclusion, β‑NF represses Dp71 expression in hepatic cells by altering binding of YY1, Sp1, and Sp3 to the Dp71 promoter. [ABSTRACT FROM AUTHOR]

Understanding drug resistance in Mycobacterium tuberculosis requires an integrated analysis of strain lineages, mutations and gene expression. Previously, we reported the differential expression of esxG, esxH, infA, groES, rpmI, rpsA and lipF genes in a sensitive M. tuberculosis strain and in a multidrug-resistant clinical isolate. Here, we have evaluated the expression of these genes in 24 clinical isolates that belong to different lineages and have different drug resistance profiles. In vitro, growth kinetics analysis showed no difference in the growth of the clinical isolates, and thus drug resistance occurred without a fitness cost. However, a quantitative reverse transcription PCR analysis of gene expression revealed high variability among the clinical isolates, including those with similar drug resistance profiles. Due to the complexity of gene regulation pathways and the wide diversity of M. tuberculosis lineages, the use of gene expression as a molecular signature for drug resistance is not straightforward. Therefore, we recommend that the expression of M. tuberculosis genes be performed individually, and baseline expression levels should be verified among several different clinical isolates, before any further applications of these findings. [ABSTRACT FROM AUTHOR]

In this study, we delineated the molecular mechanisms that modulate Dp71 expression during neuronal differentiation, using the N1E-115 cell line. We demonstrated that Dp71 expression is up-regulated in response to cAMP-mediated neuronal differentiation of these cells, and that this induction is controlled at promoter level. Functional deletion analysis of the Dp71 promoter revealed that a 5′-flanking 159-bp DNA fragment that contains Sp1 and AP2 binding sites is necessary and sufficient for basal expression of this TATA-less promoter, as well as for its induction during neuronal differentiation. Electrophoretic mobility shift and chromatin immunoprecipitation assays revealed that Sp1 and AP2α bind to their respective DNA elements within the Dp71 basal promoter. Overall, mutagenesis assays on the Sp1 and AP2 binding sites, over-expression of Sp1 and AP2α, as well as knock-down experiments on Sp1 and AP2α gene expression established that Dp71 basal expression is controlled by the combined action of Sp1 and AP2α, which act as activator and repressor, respectively. Furthermore, we demonstrated that induction of Dp71 expression in differentiated cells is the result of the maintenance of positive regulation exerted by Sp1, as well as of the loss of AP2α binding, which ultimately releases the promoter from repression. [ABSTRACT FROM AUTHOR]

Abstract: Polycyclic aromatic hydrocarbons (PAH) are the main components of emissions generated by coke oven factories and many of these chemicals are carcinogenic. The goal of this study was to examine changes in gene expression in two human cell lines, HepG2 and A549, induced by exposure to a soil extract containing PAH using microarry technology. Soil samples were obtained from the vicinity of a coke oven factory in northeastern Mexico. For comparison, the gene expression pattern induced by Benz[a]pyrene (BaP) was also analyzed. The number of altered genes by both treatments was 2-fold higher in hepatic than in pulmonary cells. Differentially-modulated genes in the two cell lines were identified and grouped by biological function using genomic databases. A group of nine genes up- and down-regulated by either the PAH extract or BaP were selected for validation by real-time PCR. The cellular functions of these PAH-responsive genes included: xenobiotic metabolism (CYP1A1 and CYP1B1), DNA repair (ERCC5), oxidative stress response and cell proliferation (FTH1 and PRDX1), protein degradation (PSMD7), ion transport (FXYD3), steroid biosynthesis (FDFT1), and signaling pathways (PTGER3). The real-time PCR analysis confirmed most of the microarray data with significant correlation. Additional studies are required to determine the mechanisms involved in the PAH-mediated modulation of these genes and to associate these changes with human health. [Copyright &y& Elsevier]