AK007836 encodes a noncoding RNA (ncRNA) consist-ing of 2 exons. Since AK007836 is located just upstream of Pcna and transcribed in the opposite direction to that of Pcna, we analyzed its expression pattern. Both ncRNA and Pcna expressions were detected in in vitro and in vivo cells, showing a positive correlation. A 177 bp region se-parating the first exons of Pcna and AK007836 has a bidirectional promoter activity. When the expression of ncRNA was reduced by siRNA, Pcna expression was also reduced in normal cells, but not in cancer cells. These results suggest that the ncRNA is divergently transcribed from the bidirectional promoter, positively regulating the neighboring protein-coding Pcna gene transcription, and this regulatory function is somehow disrupted in cancer cells.

Keywords: bidirectional promoter, co-expression, gene regulation, non-coding RNA, Pcna