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Biomedical subjects

M Radman

Publications and source records attributed to M Radman.

121 records · Page 7Linked to original sources
PubMedDate not supplied

recA-independent mutagenicity induced by chloroethylene oxide in E. coli.

The mechanism of mutagenicity of chloroethylene oxide (CEO), an ultimate carcinogenic metabolite of vinyl chloride, was investigated in 3 Escherichia coli strains (E. coli "multitest"). In this system, the mutagenicity of CEO was found to be mainly SOS-independent. CEO did not induce recombinational events at a detection level of about 10(-2) recombinants/survivor. Our results indicate that CEO- (or vinyl chloride-) induced bacterial mutagenesis arises mainly from miscoding DNA adducts.

Escherichia coli↗
PubMedDate not supplied

Processing of mispaired and unpaired bases in heteroduplex DNA in E. coli.

Bacteriophage lambda and phi X 174 DNAs, carrying sequenced mutations, have been used to construct in vitro defined species of heteroduplex DNA. Such heteroduplex DNAs were introduced by transfection, as single copies, into E. coli host cells. The progeny of individual heteroduplex molecules from each infective center was analyzed. The effect of the presence of GATC sequences (phi X 174 system) and of their methylation (lambda system) was tested. The following conclusions can be drawn: some mismatched base pairs trigger the process of mismatch repair, causing a localized strand-to-strand information transfer in heteroduplex DNA: transition mismatches G:T and A:C are efficiently repaired, whereas the six transversion mismatches are not always readily recognized and/or repaired. The recognition of transversion mismatches appears to depend on the neighbouring nucleotide sequence; single unpaired bases (frameshift mutation "mismatches") are recognized and repaired, some equally efficiently on both strands (longer and shorter), some more efficiently on the shorter (-1) strand; large non-homologies (about 800 bases) are not repaired by the Mut H, L, S, U system, but some other process repairs the non-homology with a relatively low efficiency; full methylation of GATC sequences inhibits mismatch repair on the methylated strand: this is the chemical basis of strand discrimination (old/new) in mismatch correction; unmethylated GATC sequences appear to improve mismatch repair of a G:T mismatch in phi X 174 DNA, but there may be some residual mismatch repair in GATC-free phi X 174, at least for some mismatches.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriophage lambda↗