To investigate the mechanism of increased expression of caspase-1 caused by exogenousHippi, observed earlier in HeLa and Neuro2A cells, in this work we identified a specific motif AAAGACATG ()101 to)93) at the caspase-1 gene upstream sequence where HIPPI could bind. Various muta-tions in this specific sequence compromised the interaction, showing the specificity of the interactions.