The homodimeric Ocr (overcome classical restriction) protein of bacteriophage T7 is a molecular mimic of double-stranded DNA and a highly effective competitive inhibitor of the bacterial type I restriction/modification system. The surface of Ocr is replete with acidic residues that mimic the phosphate backbone of DNA. In addition, Ocr also mimics the overall dimensions of a bent 24-bp DNA molec...

Little is known about the effects of single DNA methylation events on gene transcription. The ability to direct the methylation toward a single unique site within a genome would have broad use as a tool to study the effects of specific epigenetic changes on transcription. A targeted enzyme might also be useful in a therapy for diseases with an epigenetic component or as a means to site-specific...

In neoplastic cells, levels of DNA methyltransferase activity are often increased, and evidence is accruing to suggest an important role for this event in tumorigenesis. To evaluate this possibility further, and to investigate the contribution of increasing de novo, as opposed to maintenance, DNA methylation in mammalian cells, we expressed the bacterial HhaI methyltransferase in cultured murin...

The ocr protein, the product of gene 0.3 of bacteriophage T7, is a structural mimic of the phosphate backbone of B-form DNA. In total it mimics 22 phosphate groups over approximately 24 bp of DNA. This mimicry allows it to block DNA binding by type I DNA restriction enzymes and to inhibit these enzymes. We have determined that multiple ocr dimers can bind stoichiometrically to the archetypal ty...

The ocr protein, the product of gene 0.3 of bacteriophage T7, is a structural mimic of the phosphate backbone of B-form DNA. In total it mimics 22 phosphate groups over ~24 bp of DNA. This mimicry allows it to block DNA binding by type I DNA restriction enzymes and to inhibit these enzymes. We have determined that multiple ocr dimers can bind stoichiometrically to the archetypal type I enzyme, ...

conclusions: this study detected multiple drug resistance in pseudomonas aeruginosa including resistance to β-lactams, aminoglycosides, and fluoroquinolones. therefore, identification of drug resistance patterns in p. aeruginosa and detection of pan-resistant producing isolates are of great importance in prevention and control of infections in burn center ward. background: serious infections by...

The enzyme O6-methylguanine-DNA methyltransferase repairs alkylation-induced DNA damage, O6-methylguanine and O4-methylthymine, the former being formed more frequently. Previously, by means of gene targeting, we generated mice in which alleles for methyltransferase were disrupted. We now use these mouse lines, which are totally deficient in methyltransferase activity, to examine protective effe...

DNA methylation regulates gene expression in many organisms. In eukaryotes, DNA methylation is associated with gene repression, while it exerts both activating and repressive effects in the Proteobacteria through largely locus-specific mechanisms. Here, we identify a critical DNA methyltransferase in M. tuberculosis, which we term MamA. MamA creates N⁶-methyladenine in a six base pair recogniti...

Chromatin can adopt a decondensed state linked to gene transcription (euchromatin) and a condensed state linked to transcriptional repression (heterochromatin). These states are controlled by epigenetic modulators that are active on either the DNA or the histones and are tightly associated to each other. Methylation of both DNA and histones is involved in either the activation or silencing of g...

DNA methyltransferase inhibitors represent promising new drugs for cancer therapies. The first of these compounds (5-azacytidine, Vidaza) has recently been approved as an antitumor agent, and others are presently in various stages of their preclinical or clinical development. Most of the archetypal inhibitors have been established and characterized in different experimental systems, which has t...