MCM3AP is transcribed from a promoter within an intron of the overlapping gene for GANP.

MCM3 acetylase (MCM3AP) and germinal-centre associated nuclear protein (GANP) are transcribed from the same locus and are therefore confused in databases because the MCM3 acetylase DNA sequence is contained entirely within the much larger GANP sequence and the entire MCM3AP sequence is identical to the carboxy terminus of GANP. Thus, the MCM3AP and GANP genes are read in the same reading frame and MCM3AP is an N-terminally truncated region of GANP. However, we show here that MCM3AP and GANP are different proteins, occupying different locations in the cell and transcribed from different promoters. Intriguingly, a promoter for MCM3AP lies within an intron of GANP. This report is an interesting example in nature of two separate gene products from the same locus that perform two entirely different functions in the cell. Therefore, to avoid further confusion, they should now be referred to as separate but overlapping genes.