CENP-B: Cornerstone of Kinetochores in Centromeres of Human Chromosomes

Each chromosome contains a centromere, the site at which the kinetochore assembles to ensure accurate chromosome segregation during cell division. Centromeric chromatin, which anchors the kinetochore, includes three core proteins: Centromere Protein A (CENP-A), CENP-B, and CENP-C. Among these, CENP-B is unique for its sequence-specific DNA binding to a 17-base pair element known as the CENP-B box within the alpha-satellite DNA. CENP-B contains an N-terminal DNA-binding domain and a C-terminal dimerization domain that together enable juxtaposition of distant CENP-B boxes and promote higher-order centromeric structure. CENP-B also interacts directly with CENP-A and CENP-C, thereby facilitating kinetochore assembly. The CENP-B box includes two CpG dinucleotides that, when methylated, reduce CENP-B binding and limit recruitment of CENP-A and CENP-C. The recently completed human genome assembly (T2T-CHM13) revealed centromeric regions with low CpG methylation, termed centromere dip regions, that coincide with active, unmethylated CENP-B boxes. The uniform density of these unmethylated sites across chromosomes contributes to balanced kinetochore-spindle attachment. The CENP-B gene shows no pathogenic alterations in the American Association for Cancer Research (AACR) GENIE cancer cohort (211,526 patients), underscoring its conserved role in chromosome stability.