HBP1 is a transcriptional repressor that binds to the promoter region of target genes. This protein plays a role in the regulation of the cell cycle and of the Wnt pathway. It binds preferentially to the sequence 5'-TTCATTCATTCA-3'. Binding to the H1F0 promoter, HBP1 is enhanced by interaction with RB1. The protein also can disrupt the interaction between DNA and TCF4.