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WOS:000452343100012; International audience; Background: Deinococcus radiodurans R1 (DR) survives conditions of extreme desiccation, irradiation and exposure to genotoxic chemicals, due to efficient DNA breaks repair, also through Mn2+ protection of DNA repair enzymes. Methods: Possible annotated domains of the DR1533 locus protein (Shp) were searched by bioinformatic analysis. The gene was cloned and expressed as fusion protein. Band-shift assays of Shp or the SRA and HNH domains were performed on oligonucleotides, genomic DNA from E. coif and DR. slip knock-out mutant was generated by homologous recombination with a kanamycin resistance cassette. Results: DR1533 contains an N-terminal SRA domain and a C-terminal HNH motif (SRA-HNH Protein, Shp). Through its SRA domain, Shp binds double-strand oligonucleotides containing 5mC and 5hmC, but also unmethylated and mismatched cytosines in presence of Mn2+. Shp also binds to Escherichia coli dcm(+) genomic DNA, and to cytosine unmethylated DR and E. coli dcm(-) genomic DNAs, but only in presence of Mn2+. Under these binding conditions, Shp displays DNAse activity through its HNH domain. Shp KO enhanced \textgreater 100 fold the number of spontaneous mutants, whilst the treatment with DNA double strand break inducing agents enhanced up to 3-log the number of survivors. Conclusions: The SRA-HNH containing protein Shp binds to and cuts 5mC DNA, and unmethylated DNA in a Mn2+ dependent manner, and might be involved in faithful genome inheritance maintenance following DNA damage. General significance: Our results provide evidence for a potential role of DR Shp protein for genome integrity maintenance, following DNA double strand breaks induced by genotoxic agents.

""Peroxisome proliferator-activated receptor gamma (PPARG) inactivation has been identified as an important step in colorectal cancer (CRC) progression, although the events involved have been partially clarified. UHRF1 is emerging as a cofactor that coordinates the epigenetic silencing of tumor suppressor genes, but its role in CRC remains elusive. Here, we report that UHRF1 negatively regulates PPARG and is associated with a higher proliferative, clonogenic and migration potential. Consistently, UHRF1 ectopic expression induces PPARG repression through its recruitment on the PPARG promoter fostering DNA methylation and histone repressive modifications. In agreement, UHRF1 knockdown elicits PPARG re-activation, accompanied by positive histone marks and DNA demethylation, corroborating its role in PPARG silencing. UHRF1 overexpression, as well as PPARG-silencing, imparts higher growth rate and phenotypic features resembling those occurring in the epithelial-mesenchymal transition. In our series of 110 sporadic CRCs, high UHRF1-expressing tumors are characterized by an undifferentiated phenotype, higher proliferation rate and poor clinical outcome only in advanced stages III-IV. In addition, the inverse relationship with PPARG found in vitro is detected in vivo and UHRF1 prognostic significance appears closely related to PPARG low expression, as remarkably validated in an independent dataset. The results demonstrate that UHRF1 regulates PPARG silencing and both genes appear to be part of a complex regulatory network. These findings suggest that the relationship between UHRF1 and PPARG may have a relevant role in CRC progression.Oncogene advance online publication, 30 January 2012; doi:10.1038\\\/onc.2012.3.""

HMG-CoA reductase inhibitors, such as Lovastatin and Simvastatin, cause cell cycle arrest by interfering with the mitogenic activity of mitogens present in culture media. Cells are induced to pause in G1 and can readily resume growth upon removal of the enzymatic block. Estrogens, acting via their nuclear receptor, are mitogens for different normal and transformed cell types, where they foster cell cycle progression and cell division. In estrogen-responsive MCF-7 human breast cancer cells, but not in non responsive cells, 17 beta-estradiol (E2) induces cells arrested with Lovastatin or Simvastatin to proliferate in the presence of inhibitor, without restoring HMG-CoA reductase activity or affecting the protein prenylation pattern. Mitogenic stimulation of G1-arrested MCF-7 cells with E2 includes primary transcriptional activation of c-fos, accompanied by transient binding in vivo of the estrogen receptor and/or other factors to the ERE and the estrogen-responsive DNA region of this proto-oncogene, as detected by dimethylsulphate genomic footprinting analysis. Mitogenic stimulation of growth-arrested MCF-7 cells by E2 occurs, under these conditions, without evident activation of ERK-1 and -2 kinases, and thus independently from the mitogen-responsive signal transduction pathways that converge on these enzymes.

Inhibitors of 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase, such as Simvastatin and Lovastatin, reduce the rate of DNA synthesis and proliferation of a wide variety of cell types in vitro, by inducing a cell cycle arrest in G1. In estrogen-free medium, DNA synthesis is reduced by more that 90% following exposure of normal and transformed human breast epithelia] cells to 20 microM Simvastatin or Lovastatin for 24 to 42 hrs. We show here that stimulation of estrogen responsive MCF-7 cells with nanomolar concentrations of 17beta-estradiol (E2) prevents inhibition of DNA synthesis by these compounds. The effect of the hormone is antagonized by both steroidal and non steroidal antiestrogens, and it is not detectable in estrogen receptor-negative MCF-10a cells. Cell cycle analysis demonstrates that HMG-CoA reductase inhibitors are unable to induce G1 arrest of MCF-7 cells in the presence of E2.