当前位置： SCI文献检索 > CARCINOGENESIS期刊下所有文献 > Human O(6)-alkylguanine-DNA alkyltransferase: protection against alkylating agents and sensitization to dibromoalkanes.

Human O(6)-alkylguanine-DNA alkyltransferase: protection against alkylating agents and sensitization to dibromoalkanes.

Abstract：

:O(6)-alkylguanine-DNA alkyltransferase (AGT) is a suicide protein that corrects DNA damage by alkylating agents and may also serve to activate environmental carcinogens. We expressed human wild-type and two active mutant AGTs in bacteria that lack endogenous AGT and are also defective in nucleotide excision repair, to examine the ability of the AGTs to protect Escherichia coli from DNA damage by different types of alkylating agents and, oppositely, to sensitize cells to the genotoxic effects of dibromoalkanes (DBAs). Control bacteria carrying the cloning vector alone were extremely sensitive to mutagenesis by low, noncytotoxic doses of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Expression of human wild-type AGT prevented most of this enlarged susceptibility to MNNG mutagenesis. Oppositely, cell killing required much higher MNNG concentrations and prevention by wild-type AGT was much less effective. Mutants V139F and V139F/P140R/L142M protected bacteria against MNNG-induced cytotoxicity more effectively than the wild-type AGT, but protection against the less stringent mutagenesis assay was variable. Subtle differences between wild-type AGT and the two mutant variants were further revealed by assaying protection against mutagenesis by more complex alkylating agents, such as N-ethyl-N-nitrosourea and 1-(2-chloro- ethyl)-3-cyclohexyl-1-nitrosourea. Unlike wild-type and V139F, the triple mutant variant, V139F/P140R/L142M was unaffected by the AGT inhibitor, O(6)-benzylguanine. Wild-type AGT and V139F potentiated the genotoxic effects of DBAs; however, the triple mutant virtually failed to sensitize the bacteria to these agents. These experiments provide evidence that in addition to the active site cysteine at position 145, the proline at position 140 might be important in defining the capacity by which AGTs modulate genotoxicity by environmentally relevant DBAs. The ability of AGTs to activate dibromoalkanes suggests that this DNA repair enzyme could be altered, and if expressed in tumors might be lethal by enhancing the activation of specific chemotherapeutic prodrugs.

journal_name

Carcinogenesis

journal_title

Carcinogenesis

authors

Abril N,Luque-Romero FL,Christians FC,Encell LP,Loeb LA,Pueyo C

doi

10.1093/carcin/20.11.2089

keywords:

subject

Has Abstract

pub_date

1999-11-01 00:00:00

pages

2089-94

issue

eissn

0143-3334

issn

1460-2180

journal_volume

pub_type

杂志文章

在线工具

Human O(6)-alkylguanine-DNA alkyltransferase: protection against alkylating agents and sensitization to dibromoalkanes.