Bifunctional Alkylating Agent-Mediated MGMT-DNA Cross-linking and its Proteolytic Cleavage in 16HBE Cells.

Bifunctional Alkylating Agent-Mediated MGMT-DNA Cross-linking and its Proteolytic Cleavage in 16HBE Cells. Toxicol Appl Pharmacol. 2016 Jun 21; Authors: Cheng J, Ye F, Dan G, Zhao Y, Wang B, Zhao J, Sai Y, Zou Z Abstract Nitrogen mustard (NM), a bifunctional alkylating agent (BAA), contains two alkyl arms and can act as a cross-linking bridge between DNA and protein to form a DNA-protein cross-link (DPC). O(6)-methylguanine-DNA methyltransferase (MGMT), a DNA repair enzyme for alkyl adducts removal, is found to enhance cell sensitivity to BAAs and to promote damage, possibly due to its stable covalent cross-linking with DNA mediated by BAAs. To investigate MGMT-DNA cross-link (mDPC) formation and its possible dual roles in NM exposure, human bronchial epithelial cell line 16HBE was subjected to different concentrations of HN2, a kind of NM, and we found mDPC was induced by HN2 in a concentration-dependent manner, but the mRNA and total protein of MGMT were suppressed. As early as 1 h after HN2 treatment, high mDPC was achieved and the level maintained for up to 24 h. Quick total DPC (tDPC) and γ-H2AX accumulation were observed. To evaluate the effect of newly predicted protease DVC1 on DPC cleavage, we applied siRNA of MGMT and DVC1, MG132 (proteasome inhibitor), and NMS-873 (p97 inhibitor) and found that proteolysis plays a role. DVC1 was proven to be more important in the cleavage of mDPC than tDPC in a p97-dependent manner. HN2 e...
Source: Toxicology and Applied Pharmacology - Category: Toxicology Authors: Tags: Toxicol Appl Pharmacol Source Type: research