Principal Investigator Iain Cheeseman
A subset of kinetochore components stably associates with centromeric DNA to provide a platform to assemble the entire kinetochore structure. Our laboratory is analyzing the nature of the kinetochore-DNA interface and how these DNA binding proteins direct kinetochore assembly. In vertebrates, centromeres are not defined by specific sequences and are instead controlled by epigenetic mechanisms that involve specialized nucleosomes containing the histone H3 variant CENP-A. Although prior work demonstrated that CENP-A is necessary for centromere specification, in human cells CENP-A is not sufficient for kinetochore assembly. As part of an ongoing collaboration with Tatsuo Fukagawa’s lab, we identified the histone fold-containing CENP-T-W-S-X complex as a key, conserved DNA binding protein complex at centromeres. CENP-T plays an essential role in kinetochore assembly. In fact, we demonstrated that artificial targeting of CENP-T to an ectopic locus is sufficient to direct assembly of a functional kinetochore-like structure in the absence of CENP-A. Interestingly, although the CENP-T-W-S-X complex does not display strong sequence similarity to histones, crystallographic analyses revealed that this complex has structural similarity to canonical nuclesomes. This suggests that the CENP-T-W-S-X complex could provide a chromatin foundation at centromeres in parallel to CENP-A. Our current focus is to determine how CENP-A and the CENP-T-W-S-X complex are targeted to centromeres.