Moreover, when the construct was co-transfected with p53- or p63-specific siRNAs (S2a and S2b Fig), this effect was markedly attenuated (Fig 2b), indicating that the PV-associated rs17315309 risk allele increases ST18 promoter activity in a p53-/p63-dependent manner. This evidence concerns the gene TP63 and acquired polycythemia vera.