Models for novel function of ISWI and RanGTP. (A) A novel role of ISWI in mitosis. In interphase, ISWI localizes inside nuclei and binds to chromosomes for chromatin remodeling. In mitosis, the majority of ISWI dissociates from chromosomes and localizes on spindle poles and microtubules. ISWI is essential for RanGTP-dependent microtubule stabilization in anaphase. (B) A novel role of chromosomes and RanGTP in anaphase. Chromosomes produce RanGTP gradient around them throughout mitosis. RanGTP induces spindle assembly in metaphase and nuclear envelope and pore complex assembly in telophase. Distinctly, RanGTP stabilizes and maintains spindle MTs in anaphase by activating ISWI. This is essential for chromosomes to be segregated along the MTs. Chromosomes and RanGTP probably induce additional events in mitosis in order to ensure chromosome segregation and cell division.