Based on limited published evidence, KATNBL1 is a regulatory subunit that controls microtubule-severing activity of katanin A subunits (KATNA1 and KATNAL1) in a concentration-dependent manner. KATNBL1 localizes to spindle poles during mitosis and associates with katanin catalytic subunits to regulate their microtubule-severing function 1. During interphase, KATNBL1 is sequestered in the nucleus via an N-terminal nuclear localization signal and may coordinate with KATNB1 to modulate katanin activity during cell division and microtubule remodeling 1.