EVIDENCE FOR THE SIMULTANEOUS EXPRESSION OF ALTERNATIVELY SPLICED ALKYLPURINE N-GLYCOSYLASE TRANSCRIPTS IN HUMAN TISSUES AND CELLS

We have isolated a novel human alkylpurine N-glycosylase (APNG) cDNA from a placental library by screening with an oligonucleotide based on the published sequence of the human liver cDNA encoding this protein. The nucleotide sequences of the two cDNAs were essentially identical, but the 5' untranslated region of the new sequence was truncated and the 5'-terminal 92 nucleotides of the novel cDNA were different, indicating the possibility of alternative transcripts. This region included a portion of the open reading frame, so that the predicted protein was truncated and the seven N-terminal amino acids differed from the published sequence for APNG. PCR amplification of reverse transcribed mRNA, using 5' primers unique to the two cDNAs and a common 3' primer showed that the alternative transcripts can be co-expressed in the same cells and tissues.