Identification and characterization of the novel protein CCDC106 that interacts with p53 and promotes its degradation.

The putative CCDC106 protein was previously identified as a p53-interacting partner by automated yeast two-hybrid screening, but its sequence and function have not been validated experimentally. Here, we identified three variant transcripts of the CCDC106 gene; these transcripts differ in their second exons due to the use of different splice acceptor site, but encode an identical protein of 280 residues. A bipartite nuclear localisation signal at residues 151-164 mediates the nuclear localisation of CCDC106. Double immunofluorescence staining revealed the colocalisation of endogenous CCDC106 and p53 protein in nuclei. The in vivo interaction between CCDC106 and p53 was confirmed by a co-immunoprecipitation assay. Furthermore, we demonstrated that CCDC106 promotes the degradation of p53 protein and inhibits its transactivity.