Base eversion and shuffling by DNA methyltransferases

AdoMet-dependent methylation, DNA methyltransferases and base flipping.

Twenty AdoMet-dependent methyltransferases (MTases) have been characterized structurally by X-ray crystallography and NMR. These include seven DNA MTases, five RNA MTases, four protein MTases and four small molecule MTases acting on the carbon, oxygen or nitrogen atoms of their substrates. The MTases share a common core structure of a mixed seven-stranded beta-sheet (6 downward arrow 7 upward a...

2-Aminopurine as a fluorescent probe for DNA base flipping by methyltransferases.

DNA base flipping, which was first observed for the C5-cytosine DNA methyltransferase M. Hha I, results in a complete removal of the stacking interactions between the target base and its neighbouring bases. We have investigated whether duplex oligodeoxynucleotides containing the fluorescent base analogue 2-aminopurine can be used to sense DNA base flipping. Using M. Hha I as a paradigm for a ba...

DNA bending induced by DNA (cytosine-5) methyltransferases.

DNA bending induced by six DNA (cytosine-5) methyltransferases was studied using circular permutation gel mobility shift assay. The following bend angles were obtained: M.BSP:RI (GG(m5)CC), 46-50 degrees; M.HAE:III (GG(m5)CC), 40-43 degrees; M.SIN:I (GGW(m5)CC), 34-37 degrees; M.SAU:96I (GGN(m5)CC), 52-57 degrees; M.HPA:II (C(m5)CGG), 30 degrees; and M.HHA:I (G(m5)CGC), 13 degrees. M. HAE:III w...

Bifunctional Prokaryotic DNA-Methyltransferases

Mammalian DNA methyltransferases.

DNA methylation is an epigenetic process affecting gene expression and chromatin organization. It can heritably silence or activate transcription of genes without any change in their nucleotide sequences, and for a long time was not recognized as an important regulatory mechanism. However, during the recent years it has been shown that improper methylation, especially hypermethylation of promot...