CGI-121 has been shown to bind to the p53-related protein kinase (PRPK) [1]. PRPK is a novel protein kinase which binds to and induces phosphorylation of the tumour suppressor protein p53. CGI-121 is part of a conserved protein complex, KEOPS. The KEOPS complex is involved in telomere uncapping and telomere elongation [2]. Interestingly this family also include archaeal homologues, formerly in the DUF509 family. A structure for these proteins has been solved by structural genomics.

1: Identification of CGI-121, a novel PRPK (p53-related protein kinase)-binding protein. Miyoshi A, Kito K, Aramoto T, Abe Y, Kobayashi N, Ueda N; Biochem Biophys Res Commun. 2003;303:399-405. PMID:12659830

2: A genome-wide screen identifies the evolutionarily conserved KEOPS complex as a telomere regulator. Downey M, Houlsworth R, Maringele L, Rollie A, Brehme M, Galicia S, Guillard S, Partington M, Zubko MK, Krogan NJ, Emili A, Greenblatt JF, Harrington L, Lydall D, Durocher D; Cell. 2006;124:1155-1168. PMID:16564010