CGI-55 interacts with nuclear proteins and co-localizes to p80-coilin positive-coiled bodies in the nucleus.

The human protein CGI-55 has been described as a chromo-helicase-DNA-binding domain protein (CHD)-3 interacting protein and was also found to interact with the 3'-region of the plasminogen activator inhibitor (PAI)-1 mRNA. Here, we used CGI-55 as a "bait" in a yeast two-hybrid screen and identified eight interacting proteins: Daxx, Topoisomerase I binding RS (Topors), HPC2, UBA2, TDG, and protein inhibitor of activated STAT (signal transducer and activator of transcription) (PIAS)-1, -3, and -y. These proteins are either structurally or functionally associated with promyelocytic leukemia nuclear bodies (PML-NBs), protein sumoylation, or the regulation of transcription.

Characterization of a new family of proteins that interact with the C-terminal region of the chromatin-remodeling factor CHD-3.

The two human proteins Ki-1/57 and CGI-55 have highly similar amino acid sequences but their functions are unknown. We analyzed them by yeast two-hybrid screens and found that they interact with the C-terminal region of the human chromatin-remodeling factor CHD-3 (chromo-helicase-DNA-binding domain protein-3). The interaction of CGI-55 and CHD-3 could be confirmed in vitro and in vivo by co-immunoprecipitations from Sf9 insect cells.