Contribution to the characterization of human kinetochore proteins CENP-C and hMis12 in vitro and in vivo
The human kinetochore assembly process is involving several proteins and molecules including DNA. However, the assembly mechanism and the exact positions of kinetochore proteins are still poorly understood. Previous report hypothesized that CENP-C localized on the surface of inner kinetochore protein and hMis12 has own loading pathway into kinetochore. CENP-C is evolutionarily conserved protein that known to have the DNA binding domain. It is thought to have role in the kinetochore assembly and regulate proper chromosome segregation. hMis12 has a role in regulating the functional centromere during the cell cycle. It is required for correct spindle morphogenesis in metaphase and maintaining the inner kinetochore structure. The efforts to detect interactions of CENP-C and hMis12 with human CENP-A, CENP-B and CENP-C proteins by in vitro assays failed. This negative result suggests the existence of mediator interactions between CENP-A, CENP-C, CENP-H, CENP-I and hMis12. hMis12 likely localizes at the surface of the inner kinetochore and it might establish a bridge between the inner and outer kinetochore during mitosis, thus CENP-C localization is hypothesized upstream of hMis12. Moreover, this study demonstrated for the first time the implication of epigenetic modification of centromere proteins during kinetochore assembly process through the association of CENP-C with SETDB1, a H3K9 methylase activity and DNA methyltransferase interaction partner. This interaction might promote specific kinetochore methylation.