RelA-associated inhibitor is a protein that in humans is encoded by the PPP1R13L gene. Regulator that plays a central role in regulation of apoptosis and transcription via its interaction with NF-kappa-B and p53/TP53 proteins. Blocks transcription of HIV-1 virus by inhibiting the action of both NF-kappa-B and SP1. Also inhibits p53/TP53 function, possibly by preventing the association between p53/TP53 and ASPP1 or ASPP2, and therefore suppressing the subsequent activation of apoptosis. Interacts with RELA NF-kappa-B subunit and with SP1 via its C-terminus part. Interacts with p53/TP53, TP63 and TP73.