Controlling Epigenetic Signaling with Dnmt1 and Dnmt3b

Wed, 02/12/2014 - 13:27

Dnmt1 belongs to the C5-methyltransferase family that repairs cytosines in dsDNA using a nucleophilic attack mechanism. Dnmt1 is the most abundant mammalian DNA methyltransferase. It is the key methylation maintenance enzyme for both DNA replication/repair and de novo methylation during somatic cell development and differentiation. It primarily acts upon CpG residues, with a preference for hemimethylated residues, but is capable of methylating unmethylated DNA more than other Dnmt enzymes. In cell division, it is essential for epigenetic inheritance because it associates with S-phase DNA replication sites to maintain the methylation pattern in newly synthesized strand. To maintain DNA methylation independently of replication, Dnmt1 routinely cycles through different states of complex formation and localization. It associates with the chromatin during both G2 and M phases, is reduced to undetectable levels at the G0 phase, and then is dramatically induced upon S-phase entry.  Researchers at the HHMI at Johns Hopkins demonstrated compelling evidence that DNA methylation and gene silencing in colorectal cancer cells is controlled by Dnmt1 and Dnmt3b (1). Their immunoblotting experiments with Dnmt1 antibody showed that cooperation between the two methyltransferases helps drive neoplastic proliferation. Robert’s group used the Dnmt1 antibody to characterize aberrant CpG island methylation and Dnmt pharmacologic inhibitors to map the function of Dnmt alleles and isotypes in cancer progression (2).

Western Blot: Dnmt1 Antibody Western Blot: Dnmt1 Antibody

The Dnmt1 antibody allowed Leu, et al. to look at the effects of epigenetic silencing on downstream targets of the estrogen receptor and their implications in breast cancer genomes (3). Detailed transcriptional repression studies with the Dnmt1 antibody on the stem cell protein SALL4 found a novel mechanism of repression through promoter co-occupation, providing insight into stem cell self-renewal processes (4). A table isotope labeling by amino acids in cell culture (SILAC) proteomic analysis using the Dnmt1 antibody was performed by Grau’s group on bladder cancer cells (5). Out of 289 differentially expressed proteins, they focused on the ubiquitination protein Cul3, and determined that Cul3 downregulation of key cytoskeletal proteins such as ezrin, filamin, and caveolin increases the invasive and proliferative potential of cells.

  1. PMID: 11932749
  2. PMID: 12496760
  3. PMID: 15548683
  4. PMID: 22128185
  5. PMID: 23308193

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