The 5'-flanking regions of the sea anemone, Aiptasia pulchella (ap) ARF1 gene showed the absence of a TATA box. The transcriptional start site determined by 5' rapid amplification of cDNA ends (5'RACE) is located 75 base pairs upstream of the translational start site. Transfection experiments in HeLa and COS-7 cells demonstrate that all the elements required to achieve significant basal transcription activity are located between position -208 and -88 relative to the transcriptional start site. There are three consensus initiator (Inr) elements for TATA-less promoter around the transcriptional start site of the apARF1 gene (+29, -158, and -226) that are likely to play roles in the regulation. For the apactin gene, the 5'-flanking region contains a TATA box located 30 base pairs upstream of the transcriptional start site. The transient transfection of apactin/luciferase deletion constructs revealed that the TATA box indeed is necessary for full expression.