Procainamide Is a Specific Inhibitor of DNA Methyltransferase 1

CpG island hypermethylation occurs in most cases of cancer, typically resulting in the transcriptional silencing of critical cancer genes. Procainamide has been shown to inhibit DNA methyltransferase activity and reactivate silenced gene expression in cancer cells by reversing CpG island hypermethylation. We report here that procainamide specifically inhibits the hemimethylase activity of DNA methyltransferase 1 (DNMT1), the mammalian enzyme thought to be responsible for maintaining DNA methylation patterns during replication. At micromolar concentrations, procainamide was found to be a partial competitive inhibitor of DNMT1, reducing the affinity of the enzyme for its two substrates, hemimethylated DNA and S-adenosyl-l-methionine. By doing so, procainamide significantly decreased the processivity of hemimethylated Procainamide was a inhibitor of the and of the of procainamide for DNMT1, procainamide to in cancer cells was significantly in cells and in cells was in procainamide be a in the of CpG island hypermethylation occurs in most cases of cancer, typically resulting in the transcriptional silencing of critical cancer genes. Procainamide has been shown to inhibit DNA methyltransferase activity and reactivate silenced gene expression in cancer cells by reversing CpG island hypermethylation. We report here that procainamide specifically inhibits the hemimethylase activity of DNA methyltransferase 1 (DNMT1), the mammalian enzyme thought to be responsible for maintaining DNA methylation patterns during replication. At micromolar concentrations, procainamide was found to be a partial competitive inhibitor of DNMT1, reducing the affinity of the enzyme for its two substrates, hemimethylated DNA and S-adenosyl-l-methionine. By doing so, procainamide significantly decreased the processivity of hemimethylated Procainamide was a inhibitor of the and of the of procainamide for DNMT1, procainamide to in cancer cells was significantly in cells and in cells was in procainamide be a in the of for the of cancer in found in cases of cancer in the DNA and the in cancer, the most the of CpG methylation CpG in the of genes. in DNA methylation in the transcriptional silencing of cancer and and its that DNA to its a for that in has been found to the of inhibit DNA be of the in the of a that be in of DNA in a of the to in cells DNA the of cancer the of by and to of of DNA a by the and for the of that was shown by to the of that procainamide DNA methyltransferase activity and silenced by CpG island hypermethylation the of procainamide and its of Procainamide and the to a that to to We to the and of procainamide of methyltransferase report that procainamide specifically inhibits the methyltransferase activity of DNMT1, by reducing the affinity of the enzyme for DNA and of methyltransferase activity was a in the processivity of the by and DNA cancer cells and and cancer cells a in procainamide for and DNA was the of was by DNA cells was to 1 of DNA was the DNA and to a CpG island the for for for for for was the for cancer cells in and procainamide for DNA was the and for 1 and of DNMT1, and in and by DNMT1, was by was a expression that a for a was to cells to expression expression was cells to to cells of for was by affinity cells in and by two was and to to the and was by and was to the and the to 1 1 and was the was and in cells and the was by and to was by and to of cells by to the to of the was and for the was of by by that the methyltransferase activity by hemimethylated of DNA and in 1 and 1 by of to a was and two to and the of was to and was the in the of of was by a a and was a a was and for for for for 1 for was to the 1 was to the for was to the and by and for for for hemimethylated was by was hemimethylated 1 and 1 procainamide for 1 of DNA was and the was by to a of processivity of was 1 and 1 procainamide for 1 was to the DNA and a of the to CpG island for for for for 1 for was the for processivity of was by the the of and the of by the of be of and that that the of of a was to a processivity of was the of that to by the of a of and and to processivity of 1 that of a processivity of that of the of a the the in in the of procainamide for 1 in a in shown in the the and the that for in the two was to of to shown in the of and the of the was and a to the of to a for the CpG and a CpG has been shown to of silenced by CpG island hypermethylation and inhibit DNA methyltransferase activity the of of DNA methyltransferase cancer cells and procainamide for of DNA that procainamide decreased in cells by Procainamide of cells decreased by of cells that was the of We to the methylation of the CpG of CpG methylation in the cells of decreased to to the of and methylation and significantly procainamide of cancer cells that procainamide CpG methylation 1 and to the that in cells that DNMT1, procainamide to of CpG methylation of and methylation in cells and cells procainamide for DNA was and was by of DNA cells procainamide for to the CpG cells procainamide for was by DNA by 1 and a has been to hemimethylated DNA to in the of a and a in DNMT1, to its in the methyltransferase responsible for methylation patterns during DNA replication. We the of procainamide to inhibit a hemimethylated and of the that procainamide inhibits a hemimethylated a of that the of partial competitive and of and and of and a of the in inhibitor the the in the procainamide the for DNA by significantly the of the of the and the of inhibitor the to We found that procainamide to in a partial competitive of and a of for procainamide of was for hemimethylated DNA and for procainamide of hemimethylated DNA 1 Procainamide was and procainamide of hemimethylated DNA 1 Procainamide was and procainamide of DNA 1 Procainamide was and procainamide of DNA 1 Procainamide was and procainamide a that of for its methyltransferase and We the of procainamide to inhibit the activity of the two and a hemimethylated and by that procainamide a and a in the the for for the in the that procainamide specifically inhibits the methyltransferase activity of for DNA in a Procainamide the of a has been found to a hemimethylated We that the of procainamide to inhibit a hemimethylated to the processivity of the the processivity of DNMT1, a processivity that the of activity that to methylation of hemimethylated to a of the was a a hemimethylated a processivity of of 1 procainamide to the the processivity to of the two activity and to the of and processivity of the resulting in processivity the affinity of the enzyme for in the of procainamide in two the processivity of the was to We found that a of was of of activity hemimethylated was 1 and hemimethylated 1 in the of 1 DNA was and by and by and by of a a that the of the be and of and in of activity hemimethylated in the of was and hemimethylated 1 DNA was and by and by and by of a a that the of the be the of by of has been to the activity of DNA in the of DNA the of procainamide to inhibit the activity of two substrates, a and a of the by We found that the of was to methyltransferase activity the of procainamide to the inhibit of by activity was by a to be procainamide activity DNA by of procainamide the of was 1 and a of and in the of the and to DNA in the of the by procainamide inhibits a hemimethylated to that to to hemimethylated procainamide specifically to hemimethylated that to a a hemimethylated a and a a in affinity of for and hemimethylated to the the of procainamide for and a hemimethylated procainamide inhibit to the hemimethylated in the of and the of of of procainamide the enzyme to hemimethylated was to the hemimethylated procainamide of to hemimethylated DNA of procainamide the of to was hemimethylated for 1 to and the of to was hemimethylated in the of of procainamide to and inhibitor to of was to the and of of methyltransferase We that the most of procainamide DNMT1, procainamide to in cells was significantly in cells and cells was and in methyltransferase activity that micromolar of procainamide the by procainamide inhibits We that procainamide inhibit the of activity and processivity hemimethylated DNA and by found that procainamide inhibits a hemimethylated that procainamide a partial competitive inhibitor of DNMT1, the of the enzyme for DNA and of in affinity for the the to the of the hemimethylated a enzyme to be to the DNA a that for the to be By the affinity of for DNA during procainamide of hemimethylated be by the of procainamide to DNA to DNA and for its to the enzyme in the enzyme the its and processivity in the of methylation in its DNA in affinity for the processivity of of of a to to the enzyme to the of the be and the enzyme to of hemimethylated DNA in the of two of that to the in the of a activity a activity that in procainamide a partial competitive inhibitor of DNMT1, the be to of inhibitor the that of DNA methyltransferase activity in by that DNA be by that the and to procainamide to DNA methyltransferase activity and that the of by DNA has been to in the of of of DNA was by procainamide that a in methylation a that was shown to in the of cancer procainamide to hemimethylated DNA in the of the that to in of the processivity was procainamide inhibit DNA procainamide the affinity of for DNA and during that procainamide inhibits the and the of the of procainamide DNMT1, hemimethylated and shown that of cancer cells procainamide decreased was be a been the of to CpG island hypermethylation in cancer cells cancer cells found a of the of was to the of to DNMT1, to be responsible for the of methylation in procainamide specifically inhibits DNMT1, and of the to methylation by of cells procainamide in of the CpG that in cells and to methylation methylation of the CpG island to the of that of processivity a of the of procainamide DNA methylation in a of the of procainamide for the and the was in to reactivate expression in was resulting in a in and of the of the Procainamide be a in has a of the of and has been shown to reactivate silenced by CpG island hypermethylation. be to procainamide of cells and CpG island hypermethylation in expression was in of the of in a to in of a in a of cancer by the of in a that specifically inhibits activity procainamide be a in the of procainamide be to the of its to in by that a and a and of was to by of the of in be in to and two of the of procainamide a partial competitive its to inhibit procainamide to activity to a that and procainamide was for its to DNA and the of be to a inhibitor of the of for the of cancer in found in cases of cancer in the DNA and the in cancer, the most the of CpG methylation CpG in the of genes. in DNA methylation in the transcriptional silencing of cancer and and its that DNA to its a for that in has been found to the of inhibit DNA be of the in the of a that be in of DNA in a of the to in cells DNA the of cancer the of by and DNA methyltransferase DNA methyltransferase to of of DNA a by the and for the of that was shown by to the of that procainamide DNA methyltransferase activity and silenced by CpG island hypermethylation the of procainamide and its of Procainamide and the to a that to to We to the and of procainamide of methyltransferase report that procainamide specifically inhibits the methyltransferase activity of DNMT1, by reducing the affinity of the enzyme for DNA and of methyltransferase activity was a in the processivity of the by and DNA cancer cells and and cancer cells a in procainamide for and DNA was the of was by DNA cells was to 1 of DNA was the DNA and to a CpG island the for for for for for was the for cancer cells in and procainamide for DNA was the and for 1 and of DNMT1, and in and by DNMT1, was by was a expression that a for a was to cells to expression expression was cells to to cells of for was by affinity cells in and by two was and to to the and was by and was to the and the to 1 1 and was the was and in cells and the was by and to was by and to of cells by to the to of the was and for the was of by by that the methyltransferase activity by hemimethylated of DNA and in 1 and 1 by of to a was and two to and the of was to and was the in the of of was by a a and was a a was and for for for for 1 for was to the 1 was to the for was to the and by and for for for hemimethylated was by was hemimethylated 1 and 1 procainamide for 1 of DNA was and the was by to a of processivity of was 1 and 1 procainamide for 1 was to the DNA and a of the to CpG island for for for for 1 for was the for processivity of was by the the of and the of by the of be of and that that the of of a was to a processivity of was the of that to by the of a of and and to processivity of 1 that of a processivity of that of the of a the the in in the of procainamide for 1 in a in shown in the the and the that for in the two was to of to shown in the of and the of the was and a to the of to a for the by and DNA cancer cells and and cancer cells a in procainamide for and DNA was the of was by DNA cells was to 1 of DNA was the DNA and to a CpG island the for for for for for was the for cancer cells in and procainamide for DNA was the and for 1 and of DNMT1, and in and by DNMT1, was by was a expression that a for a was to cells to expression expression was cells to to cells of for was by affinity cells in and by two was and to to the and was by and was to the and the to 1 1 and was the was and in cells and the was by and to was by and to of cells by to the to of the was and for the was of by by that the DNA methyltransferase activity by hemimethylated of DNA and in 1 and 1 by of to a was and two to and the of was to and was the in the of of was by a a and was a a was and for for for for 1 for was to the 1 was to the for was to the and by and for for for hemimethylated was by was hemimethylated 1 and 1 procainamide for 1 of DNA was and the was by to a of processivity of was 1 and 1 procainamide for 1 was to the DNA and a of the to CpG island for for for for 1 for was the for processivity of was by the the of and the of by the of be of and that that the of of a was to a processivity of was the of that to by the of a of and and to processivity of 1 that of a processivity of that of the of a the the in in the of procainamide for 1 in a in shown in the the and the that for in the two was to of to shown in the of and the of the was and a to the of to a for the CpG and a CpG has been shown to of silenced by CpG island hypermethylation and inhibit DNA methyltransferase activity the of of DNA methyltransferase cancer cells and procainamide for of DNA that procainamide decreased in cells by Procainamide of cells decreased by of cells that was the of We to the methylation of the CpG of CpG methylation in the cells of decreased to to the of and methylation and significantly procainamide of cancer cells that procainamide CpG methylation 1 and to the that in cells that DNMT1, procainamide to of CpG methylation a has been to hemimethylated DNA to in the of a and a in DNMT1, to its in the methyltransferase responsible for methylation patterns during DNA replication. We the of procainamide to inhibit a hemimethylated and of the that procainamide inhibits a hemimethylated a of that the of partial competitive and of and and of and a of the in inhibitor the the in the procainamide the for DNA by significantly the of the of the and the of inhibitor the to We found that procainamide to in a partial competitive of and a of for procainamide of was for hemimethylated DNA and for procainamide of hemimethylated DNA 1 Procainamide was and procainamide of hemimethylated DNA 1 Procainamide was and procainamide of DNA 1 Procainamide was and procainamide of DNA 1 Procainamide was and procainamide a that of for its methyltransferase and We the of procainamide to inhibit the activity of the two and a hemimethylated and by that procainamide a and a in the the for for the in the that procainamide specifically inhibits the methyltransferase activity of for DNA in a Procainamide the of a has been found to a hemimethylated We that the of procainamide to inhibit a hemimethylated to the processivity of the the processivity of DNMT1, a processivity that the of activity that to methylation of hemimethylated to a of the was a a hemimethylated a processivity of of 1 procainamide to the the processivity to of the two activity and to the of and processivity of the resulting in processivity the affinity of the enzyme for in the of procainamide in two the processivity of the was to We found that a of was of of activity hemimethylated was 1 and hemimethylated 1 in the of 1 DNA was and by and by and by of a a that the of the be and of and in of activity hemimethylated in the of was and hemimethylated 1 DNA was and by and by and by of a a that the of the be the of by of has been to the activity of DNA in the of DNA the of procainamide to inhibit the activity of two substrates, a and a of the by We found that the of was to methyltransferase activity the of procainamide to the inhibit of by activity was by a to be procainamide activity DNA by of procainamide the of was 1 and a of and in the of the and to DNA in the of the by procainamide inhibits a hemimethylated to that to to hemimethylated procainamide specifically to hemimethylated that to a a hemimethylated a and a a in affinity of for and hemimethylated to the the of procainamide for and a hemimethylated procainamide inhibit to the hemimethylated in the of and the of of of procainamide the enzyme to hemimethylated was to the hemimethylated procainamide of to hemimethylated DNA of procainamide the of to was hemimethylated for 1 to and the of to was hemimethylated in the of of procainamide to and inhibitor to Procainamide CpG and a CpG has been shown to of silenced by CpG island hypermethylation and inhibit DNA methyltransferase activity the of of DNA methyltransferase cancer cells and procainamide for of DNA that procainamide decreased in cells by Procainamide of cells decreased by of cells that was the of We to the methylation of the CpG of CpG methylation in the cells of decreased to to the of and methylation and significantly procainamide of cancer cells that procainamide CpG methylation 1 and to the that in cells that DNMT1, procainamide to of CpG methylation genes. Procainamide a has been to hemimethylated DNA to in the of a and a in DNMT1, to its in the methyltransferase responsible for methylation patterns during DNA replication. We the of procainamide to inhibit a hemimethylated and of the that procainamide inhibits a hemimethylated a of that the of partial competitive and of and and of and a of the in inhibitor the the in the procainamide the for DNA by significantly the of the of the and the of inhibitor the to We found that procainamide to in a partial competitive of and a of procainamide a that of for its methyltransferase Procainamide and We the of procainamide to inhibit the activity of the two and a hemimethylated and by that procainamide a and a in the the for for the in the that procainamide specifically inhibits the methyltransferase activity of Procainamide the of a has been found to a hemimethylated We that the of procainamide to inhibit a hemimethylated to the processivity of the the processivity of DNMT1, a processivity that the of activity that to methylation of hemimethylated to a of the was a a hemimethylated a processivity of of 1 procainamide to the the processivity to of the two activity and to the of and processivity of the resulting in processivity the affinity of the enzyme for in the of procainamide in two the processivity of the was to We found that a of was of Procainamide the of by of has been to the activity of DNA in the of DNA the of procainamide to inhibit the activity of two substrates, a and a of the by We found that the of was to methyltransferase activity the of procainamide to the inhibit of by activity was by a to be procainamide activity DNA by Procainamide to DNA in the of the by procainamide inhibits a hemimethylated to that to to hemimethylated procainamide specifically to hemimethylated that to a a hemimethylated a and a a in affinity of for and hemimethylated to the the of procainamide for and a hemimethylated procainamide inhibit to the hemimethylated in the of and the of of of procainamide the enzyme to hemimethylated was to the hemimethylated procainamide of to hemimethylated DNA of was to the and of of methyltransferase We that the most of procainamide DNMT1, procainamide to in cells was significantly in cells and cells was and in methyltransferase activity that micromolar of procainamide the by procainamide inhibits We that procainamide inhibit the of activity and processivity hemimethylated DNA and by found that procainamide inhibits a hemimethylated that procainamide a partial competitive inhibitor of DNMT1, the of the enzyme for DNA and of in affinity for the the to the of the hemimethylated a enzyme to be to the DNA a that for the to be By the affinity of for DNA during procainamide of hemimethylated be by the of procainamide to DNA to DNA and for its to the enzyme in the enzyme the its and processivity in the of methylation in its DNA in affinity for the processivity of of of a to to the enzyme to the of the be and the enzyme to of hemimethylated DNA in the of two of that to the in the of a activity a activity that in procainamide a partial competitive inhibitor of DNMT1, the be to of inhibitor the that of DNA methyltransferase activity in by that DNA be by that the and to procainamide to DNA methyltransferase activity and that the of by DNA has been to in the of of of DNA was by procainamide that a in methylation a that was shown to in the of cancer procainamide to hemimethylated DNA in the of the that to in of the processivity was procainamide inhibit DNA procainamide the affinity of for DNA and during that procainamide inhibits the and the of the of procainamide DNMT1, hemimethylated and shown that of cancer cells procainamide decreased was be a been the of to CpG island hypermethylation in cancer cells cancer cells found a of the of was to the of to DNMT1, to be responsible for the of methylation in procainamide specifically inhibits DNMT1, and of the to methylation by of cells procainamide in of the CpG that in cells and to methylation methylation of the CpG island to the of that of processivity a of the of procainamide DNA methylation in a of the of procainamide for the and the was in to reactivate expression in was resulting in a in and of the of the Procainamide be a in has a of the of and has been shown to reactivate silenced by CpG island hypermethylation. be to procainamide of cells and CpG island hypermethylation in expression was in of the of in a to in of a in a of cancer by the of in a that specifically inhibits activity procainamide be a in the of procainamide be to the of its to in by that a and a and of was to by of the of in be in to and two of the of procainamide a partial competitive its to inhibit procainamide to activity to a that and procainamide was for its to DNA and the of be to a inhibitor of the of of was to the and of of methyltransferase We that the most of procainamide DNMT1, procainamide to in cells was significantly in cells and cells was and in methyltransferase activity that micromolar of procainamide the by procainamide inhibits We that procainamide inhibit the of activity and processivity hemimethylated DNA and by We found that procainamide inhibits a hemimethylated that procainamide a partial competitive inhibitor of DNMT1, the of the enzyme for DNA and of in affinity for the the to the of the hemimethylated a enzyme to be to the DNA a that for the to be By the affinity of for DNA during procainamide of hemimethylated be by the of procainamide to DNA to DNA and for its to the enzyme in the enzyme the its and processivity in the of methylation in its DNA in affinity for the processivity of of of a to to the enzyme to the of the be and the enzyme to of hemimethylated DNA in the of two of that to the in the of a activity a activity that in procainamide a partial competitive inhibitor of DNMT1, the be to of inhibitor the that of DNA methyltransferase activity in by that DNA be by that the and to procainamide to DNA methyltransferase activity and that the of by DNA has been to in the of of of DNA was by procainamide that a in methylation a that was shown to in the of cancer procainamide to hemimethylated DNA in the of the that to in of the processivity was procainamide inhibit DNA procainamide the affinity of for DNA and during that procainamide inhibits the and the of the of procainamide DNMT1, hemimethylated and We shown that of cancer cells procainamide decreased was be a been the of to CpG island hypermethylation in cancer cells cancer cells found a of the of was to the of to DNMT1, to be responsible for the of methylation in procainamide specifically inhibits DNMT1, and of the to methylation by of cells procainamide in of the CpG that in cells and to methylation methylation of the CpG island to the of that of processivity a of the of procainamide DNA methylation in a of the of procainamide for the and the was in to reactivate expression in was resulting in a in and of the of the Procainamide be a in has a of the of and has been shown to reactivate silenced by CpG island hypermethylation. be to procainamide of cells and CpG island hypermethylation in expression was in of the of in a to in of a in a of cancer by the of in a that specifically inhibits activity procainamide be a in the of procainamide be to the of its to in by that a and a and of was to by of the of in be in to and two of the of procainamide a partial competitive its to inhibit procainamide to activity to a that and procainamide was for its to DNA and the of be to a inhibitor of the of We for the of and