Mutational Spectra of Salmonella typhimurium Revertants Induced by Chlorohydroxyfuranones, Byproducts of Chlorine Disinfection of Drinking Water

Abstract

The base substitution specificities of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), 3-chloro-4-(chloromethyl)-5-hydroxy-2(5H)-furanone (CMCF), 3,4-dichloro-5-hydroxy-2(5H)-furanone (MCA), and chloromalonaldehyde (CMA), a putative breakdown product of MCA, were examined in the hisG46 gene and in the hisG428 gene of Salmonella typhimurium using allele specific oligonucleotide hybridization. Although the compounds are structurally closely related, they induced substantially different mutation spectra: MCA and CMA caused primarily GC-->AT transitions in the hisG46 allele (target sequence CCC), in particular, at the second position of the codon in strain TA100. In TA100 the mutation spectrum of MCA was similar to that of CMA. The mutational specificity of MCA can be explained as a consequence of misincorporation opposite to cyclic etheno adducts identical to those formed by the carcinogen vinyl chloride. The spectra induced by MX and CMCF in TA100 were almost identical but distinctively different from the spectra of MCA and CMA. Both compounds induced primarily GC-->TA transversions, in particular, at the second position of the codon, and to a lesser extent in the first position of the codon. An identical site bias is induced by carcinogens such as polycyclic aromatic hydrocarbons and heterocyclic amines as a consequence of formation of (noncyclic) guanosine adducts. In hisG428 (target sequence TAA) MX induced again primarily GC-->TA transversions in Tyr tRNA genes (supC/M) and, to a lesser extent, intragenic AT-->TA transversions (TAA-->AAA). The possible involvement of guanosine and adenosine adducts in the mutational specificity of MX is addressed.

Mutation spectra of the drinking water mutagen 3-chloro-4-methyl-5-hydroxy-2(5H)-furanone (MCF) in Salmonella TA100 and TA104: Comparison to MX

“…A previous study with MX by Knasmüller et al [1996] in a strain similar to TA104 but missing the SOS repair provided by the pKM101 plasmid found results similar to ours, with most of the mutations being GC 3 TA transversions and the remaining small percentage being AT 3 TA transversions. For MCF, the MCF-A2 adducts could possibly account for the finding that 33% of the mutations induced by MCF in TA104 are AT 3 TA transversions.…”

“…For example, only 34% of human bladder tumors contain p53 mutations, and approximately 50% of these are GC 3 AT transitions at GpC sites, which likely result from spontaneous deamination of cytosine at such sites [Greenblatt et al, 1994]. Our results and those of others [DeMarini et al, 1995;Hyttinen et al, , 1996Knasmüller et al, 1996;Watanabe-Akanuma and Ohta, 1994] would predict the presence of predominantly GC 3 TA transversions in a target gene in tumors associated with the consumption of mutagenic drinking water [DeMarini et al, 1995;DeMarini, 1998]. …”

“…CMCF is also less potent in TA104 than in TA100, which is a profile similar to MX and unlike MCF. Also similar to MX, CMCF induces primarily GC 3 TA transversions in TA100 Knasmüller et al, 1996]. The mutation spectrum of CMCF in TA104 has not been reported but based on these structural considerations and mutagenicity data, we would predict CMCF to induce mutations predominantly at GC sites, similar to MX.…”

“…Molecular analyses of MX-induced revertants of Salmonella showed that MX induced primarily GC 3 TA transversions in the base-substitution strains (TA100, TA1535, and TP2428) and complex frameshifts (a frameshift with an adjacent base substitution) in the frameshift strain TA98 [DeMarini et al, 1995;Knasmüller et al, 1996]. MX also induced primarily GC 3 TA transversions in specially constructed strains of Escherichia coli [Watanabe-Akanuma and Ohta, 1994] as well as at the Hprt gene in Chinese hamster ovary (CHO) cells [Hyttinen et al, 1996].…”

Bacterial and mammalian‐cell genotoxicity of mixtures of chlorohydroxyfuranones, by‐products of water chlorination

“…The genotoxicities of the CHFs, MX, MCA, CMCF and MCF, are well known. The data on the induction of gene mutations in bacteria and in mammalian cells, and on the induction of DNA and chromosome damage in mammalian cells by the CHFs, show that there are differences in the genotoxic potency of these chemicals [Meier et al, 1986[Meier et al, , 1987aIshiguro et al, 1988;LaLonde et al, 1990LaLonde et al, , 1991Kronberg and Franzén, 1993;Niittykoski et al, 1995;Knasmüller et al, 1996;Franzén et al, 1998;Le Curieux et al, 1999;Shaughnessy et al, 2000;Mäki-Paakkanen et al, 2001a,b]. However, the maximum effect observed in the alkaline Comet assay and the chromosome aberration test with CHO cells was similar for the four compounds [Mäki-Paakkanen et al, 2001a].…”