Autophagy is the unique, regulated mechanism for the degradation of organelles. This intracellular process acts as a prosurvival pathway during cell starvation or stress and is also involved in cellular response against specific bacterial infections. Vibrio cholerae is a noninvasive intestinal pathogen that has been studied extensively as the causative agent of the human disease cholera. V. cholerae illness is produced primarily through the expression of a potent toxin (cholera toxin) within the human intestine. Besides cholera toxin, this bacterium secretes a hemolytic exotoxin termed autophagosomes ͉ LC3 ͉ Rab7 ͉ innate defense ͉ cellular microbiology

Survival of Pseudomonas aeruginosa in cystic fibrosis (CF) chronic infections is based on a genetic adaptation process consisting of mutations in specific genes, which can produce advantageous phenotypic switches and ensure its persistence in the lung. Among these, mutations inactivating the regulators MucA (alginate biosynthesis), LasR (quorum sensing) and MexZ (multidrug-efflux pump MexXY) are the most frequently observed, with those inactivating the DNA mismatch repair system (MRS) being also highly prevalent in P. aeruginosa CF isolates, leading to hypermutator phenotypes that could contribute to this adaptive mutagenesis by virtue of an increased mutation rate. Here, we characterized the mutations found in the mucA, lasR, mexZ and MRS genes in P. aeruginosa isolates obtained from Argentinean CF patients, and analyzed the potential association of mucA, lasR and mexZ mutagenesis with MRS-deficiency and antibiotic resistance. Thus, 38 isolates from 26 chronically infected CF patients were characterized for their phenotypic traits, PFGE genotypic patterns, mutations in the mucA, lasR, mexZ, mutS and mutL gene coding sequences and antibiotic resistance profiles. The most frequently mutated gene was mexZ (79%), followed by mucA (63%) and lasR (39%) as well as a high prevalence (42%) of hypermutators being observed due to loss-of-function mutations in mutL (60%) followed by mutS (40%). Interestingly, mutational spectra were particular to each gene, suggesting that several mechanisms are responsible for mutations during chronic infection. However, no link could be established between hypermutability and mutagenesis in mucA, lasR and mexZ, indicating that MRS-deficiency was not involved in the acquisition of these mutations. Finally, although inactivation of mucA, lasR and mexZ has been previously shown to confer resistance/tolerance to antibiotics, only mutations in MRS genes could be related to an antibiotic resistance increase. These results help to unravel the mutational dynamics that lead to the adaptation of P. aeruginosa to the CF lung.

We describe a novel human cDNA isolated by target site screening of a placental expression library, using as a probe, an essential element of a TATA box-less promoter corresponding to a pregnancy-specific glycoprotein gene. The cDNA encoded a predicted protein of 290 amino acids, designated core promoter-binding protein (CPBP), which has three zinc fingers (type Cys 2 -His 2 ) at the end of its C-terminal domain, a serine/threonine-rich central region and an acidic domain lying within the N-terminal region. Additional sequence analysis and data base searches revealed that only the zinc finger domains are conserved (60 -80% identity) in other transcription factors. In cotransfection assays, CPBP increased the transcription from a minimal promoter containing its natural DNA-binding site. Moreover, a chimeric protein between CPBP and Gal4 DNA binding domain also increased the activity of an heterologous reporter gene containing Gal4 DNA binding sites. The tissue distribution analysis of CPBP mRNA revealed that it is differentially expressed with an apparent enrichment in placental cells. The DNA binding and transcriptional activity of CPBP, in conjunction with its expression pattern, strongly suggests that this protein may participate in the regulation and/or maintenance of the basal expression of PSG and possibly other TATA box-less genes.The molecular mechanisms involved in the transcription of eukaryotic genes are controlled by the ordered interplay of DNA-protein and protein-protein contacts. The factors responsible for basal RNA-polymerase II transcription reaction are the core promoter elements and the general transcription factors (1, 2). In addition, the regulation of transcription rates results from the combined action of activating and repressing proteins that are brought to promoters, enhancers, and silencers through their interactions with specific sequences and sub-