Implication of Protein Kinase C in the Regulation of DNA Mismatch Repair Protein Expression and Function

Odile Humbert,Thierry Hermine,Hélène Hernandez,Thomas Bouget,Janick Selves,Guy Laurent,Bernard Salles,Dominique Lautier

doi:10.1074/jbc.m103451200

Odile Humbert, Thierry Hermine + Show 6 more

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https://doi.org/10.1074/jbc.m103451200

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Abstract

The DNA mismatch repair (MMR) proteins are essential for the maintenance of genomic stability of human cells. Compared with hereditary or even sporadic carcinomas, MMR gene mutations are very uncommon in leukemia. However, genetic instability, attested by either loss of heterozygosity or microsatellite instability, has been extensively documented in chronic or acute malignant myeloid disorders. This observation suggests that in leukemia some internal or external signals may interfere with MMR protein expression and/or function. We investigated the effects of protein kinase C (PKC) stimulation by 12-O-tetradecanoylphorbol-13-acetate (TPA) on MMR protein expression and activity in human myeloid leukemia cell lines. First, we show here that unstimulated U937 cells displayed low level of PKC activity as well as MMR protein expression and activity compared with a panel of myeloid cell lines. Second, treatment of U937 cells with TPA significantly increased (3-5-fold) hMSH2 expression and, to a lesser extent, hMSH6 and hPMS2 expression, correlated to a restoration of MMR function. In addition, diacylglycerol, a physiological PKC agonist, induced a significant increase in hMSH2 expression, whereas chelerythrine or calphostin C, two PKC inhibitors, significantly decreased TPA-induced hMSH2 expression. Reciprocally, treatment of HEL and KG1a cells that exhibited a high level of PKC expression, with chelerythrine significantly decreased hMSH2 and hMSH6 expression. Moreover, the alteration of MMR protein expression paralleled the difference in microsatellite instability and cell sensitivity to 6-thioguanine. Our results suggest that PKC could play a role in regulating MMR protein expression and function in some myeloid leukemia cells.

Highlights

DNA mismatch repair (MMR)1 plays an important role in the maintenance of genomic integrity, as it corrects replicative mismatches that escape DNA polymerase proofreading
We investigated the effects of protein kinase C (PKC) stimulation by 12-O-tetradecanoylphorbol-13-acetate (TPA) on MMR protein expression and activity in human myeloid leukemia cell lines
Our results suggest that PKC could play a role in regulating MMR protein expression and function in some myeloid leukemia cells

Summary

Introduction

DNA mismatch repair (MMR) plays an important role in the maintenance of genomic integrity, as it corrects replicative mismatches that escape DNA polymerase proofreading. Different mechanisms are involved in the MMR inactivation process related to the development of cancer: (i) a first mutation, either germinal (hereditary cancer) or somatic (sporadic cancer), followed by another somatic event [18]; (ii) an epigenetic silencing mechanism such as the loss of hMLH1 expression associated with promoter methylation of the hMLH1 gene [19, 20]; (iii) a deregulation of the hMSH3 expression such as an overexpression of hMSH3 by gene amplification that sequesters hMSH2 into the hMutS␤ complex, resulting in hMutS␣ activity deficiency [21, 22]. Investigations on the presence of mutations in MMR genes have shown that these mutations are uncommon events in leukemia [36] These observations show that MMR deficiency is rarely involved in leukemia cell genetic instability. The potential involvement of PKC activation on the expression of MMR protein should be considered

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