p73, the gene for a protein related to the tumor suppressor p53, encodes several variants which bear distinct carboxy-terminal structures as a result of alternative splicing. We and others showed that these splicing variants have different transcriptional effects on promoters with a p53-binding consensus sequence (p53BCS). Here we show that when transiently overexpressed, p73alpha but not p73beta activated several minimal promoters without the p53BCS, while p73gamma and p73epsilon activated them to a much lesser extent than p73alpha, and p53 suppressed the promoters without p53BCS as reported previously. Moreover, the results of RNase protection and RNA transfection assays suggested that this activation occurred at the transcriptional level. Deletion analysis of p73alpha revealed that the transactivation domain of p73 was not involved in this activity and the C-terminal region of p73alpha which is a specific structure of this variant was essential, suggesting that this phenomenon occurs independent of the transactivation activity of p73alpha and that the C-terminal extension of p73alpha may affect the basal level of transcription.