Identification and characterization of a novel antisense RNA transcribed from the opposite strand of the human blood group ABO gene.

BACKGROUND

To elucidate the molecular basis of control of the ABO gene in cell type-specific expression, during normal cell differentiation, and in cancer cells lacking A/B antigen, the mechanisms responsible for regulation of human ABO gene expression have been studied. Recently, naturally occurring antisense transcriptions have been reported to regulate gene expression through a variety of biological mechanisms. Therefore, RNA transcribed from the opposite strand of the ABO gene was investigated.

STUDY DESIGN AND METHODS

The presence of antisense RNA to the ABO-coding strand in human cancer cell lines and normal tissues was examined by strand-specific reverse transcription-polymerase chain reaction. The 5'- and 3'-ends of the transcript were determined by the rapid amplification of cDNA ends (RACE) system. KATOIII cells were treated with mithramycin A, followed by quantitative analysis of both sense and antisense ABO transcripts.

RESULTS

The endogenous antisense RNA to the ABO coding strand was found to start within the first intron of the ABO gene, and the expression coincided with ABO gene expression in various cultured cells and normal tissues. This novel gene was named ABOAS. Treatment of KATOIII cells with mithramycin A repressed transcription from the ABO exon 1 promoter, while it increased the ABOAS transcript.

CONCLUSION

These results suggest that ABOAS transcribed from the opposite strand of the ABO gene might be involved in the regulation of ABO gene expression.