Walsh, E.; Stephens, A. D.

In mitosis the duplicated genome is aligned and accurately segregated between daughter nuclei. CTCF is a chromatin looping protein in interphase with an unknown role in mitosis. We previously published data showing that CTCF constitutive knockdown causes mitotic failure, but the mechanism remains unknown. To determine the role of CTCF in mitosis, we used a CRISPR CTCF auxin inducible degron cell line for rapid degradation. CTCF degradation for 3 days resulted in increased failure of mitosis and decreased circularity in post-mitotic nuclei. Upon CTCF degradation CENP-E is still recruited to the kinetochore and there is a low incidence of polar chromosomes which occur upon CENP-E inhibition. Instead, immunofluorescence imaging of mitotic spindles reveals that CTCF degradation causes increased intercentromere distances and a wider and more disorganized metaphase plate, a disruption of key functions of the pericentromere. These results are similar to partial loss of cohesin, an established component of the pericentromere. Thus, we reveal that CTCF is a key maintenance factor of pericentromere function, successful mitosis, and post-mitotic nuclear shape.