CHROMOSOMAL LOCALIZATIONS AND MOLECULAR ANALYSIS OF TDG GENE-RELATED SEQUENCES

The human mismatch-specific thymine DNA glycosylase gene, TDG, encodes a 60-kDa polypeptide able to correct G/T mispairs arising from the de amination of B-methylcytosine. We localized by FISH three different TD G-related lambda genomic clones, lambda 8, lambda 11, and lambda 12 on chromosome 12. PCR and sequence analyses revealed that only lambda 11 , localized at 12q24.1, contained the coding gene. We characterized th e intron-exon boundaries of the portion of the gene contained in the l ambda clone and identified a CA dinucleotide repeat in one intron. Nor thern blot analysis showed that TDG is expressed at approximately the same level in all human tissues analyzed. SSCP analysis of 50 tumor an d corresponding normal tissue DNAs from lung cancer patients did not r eveal the presence of any functional mutation, An abnormal SSCP patter n in one sample proved to be a polymerphism after sequencing and RFLP analysis. (C) 1997 Academic Press.