Analysis of point mutations in HPRT mutant T-lymphocytes derived from coke-oven workers

We studied mutations in exon 3 of the hypoxanthine-guanine phosphoribosyltransferase (HPRT) locus in 113 6-thioguanine-resistant T-cell clones derived from coke-oven workers and control subjects in order to analyse possible changes in the mutational spectrum associated with the exposure to polycyclic aromatic hydrocarbons (PAHs). In 99 mutants, HPRT exon 3 was analysed by means of genomic polymerase chain reaction (PCR) and single-strand conformation polymorphism (SSCP). Products for which SSCP indicated the presence of a mutation were further analysed by DNA sequencing. In addition, HPRT cDNA from 14 clones was analysed by reverse transcription (RT) PCR and DNA sequencing. In total, 18/113 mutants (16%) had a mutation in exon 3. This frequency was similar in PAH-exposed (9/57) and non-exposed (9/56) subjects. Base substitutions caused 14 mutations at 13 different sites. Three +/- 1 bp frameshifts and one 6 bp deletion were identified. No significant differences between PAH-exposed and non-exposed workers were observed in this limited mutational spectrum. These results indicate that deletions/insertions at the HPRT exon 3 account for 22% of the mutations, and base substitutions for 78%.