TIPT2 and geminin interact with basal transcription factors to synergize in transcriptional regulation.

The re-replication inhibitor Geminin binds to several transcription factors including homeodomain proteins, and to members of the polycomb and the SWI/SNF complexes. Here we describe the TATA-binding protein-like factor-interacting protein (TIPT) isoform 2, as a strong binding partner of Geminin. TIPT2 is widely expressed in mouse embryonic and adult tissues, residing both in cyto- and nucleoplasma, and enriched in the nucleolus. Like Geminin, also TIPT2 interacts with several polycomb factors, with the general transcription factor TBP (TATA box binding protein), and with the related protein TBPL1 (TRF2). TIPT2 synergizes with geminin and TBP in the activation of TATA box-containing promoters, and with TBPL1 and geminin in the activation of the TATA-less NF1 promoter. Geminin and TIPT2 were detected in the chromatin near TBP/TBPL1 binding sites. Together, our study introduces a novel transcriptional regulator and its function in cooperation with chromatin associated factors and the basal transcription machinery.