Involvement of Cenp-F in interphase chromatin organization possibly through association with DNA-dependent protein kinase.

Cenp-F (also named mitosin) is a 350-kDa human kinetochore protein important for the mitotic progression. It is also a nuclear matrix protein in interphase cells. Here, we showed that overexpression of N-terminal deletion mutants of Cenp-F containing the C-terminal 112 residues induced chromatin condensation into numerous aggregates of varying sizes in interphase nucleus, colocalizing with the exogenous proteins. In situ hybridization using whole chromosome painting probes indicated that the chromatin aggregates were not prematurely condensed individual chromosomes. Neither were they due to apoptosis. We provided evidence showing association of Cenp-F with certain regions of interphase chromatin fibers. Cenp-F associated with the DNA-dependent protein kinase (DNA-PK), a trimeric protein complex critical for genome homeostasis. Moreover, the DNA-PK association activity of Cenp-F mutants correlated with their ability to induce chromatin aggregation. These results imply a role of Cenp-F in organization of interphase chromatin through association and possibly regulation of DNA-PK.