Crumbs and Xpd regulate mitotic motor kinesin-5 for chromosome segregation in Drosophila

Abstract

The formation and maintenance of bipolar spindles is essential for chromosome segregation during mitosis. Xeroderma pigmentosum D (Xpd) is involved in proper chromosome segregation. Crumbs (Crb) functions together with Xpd and its partner Galla during nuclear division in Drosophila embryogenesis. It is unknown how these proteins regulate mitosis. Here, we show that Crb, Galla and Xpd interact with Klp61F, the Drosophila mitotic kinesin-5, to regulate mitosis. Crb and Klp61F are co-localized to spindle during nuclear division. Spindle defects caused by abnormal Crb functions were suppressed by overexpressing Klp61F. Abnormal mitosis caused by silencing of Galla-2 or Xpd were also restored by overexpressing Klp61F. Crb, Galla-2 and Xpd form a complex with Klp61F. Depletion of Galla-2 or Xpd results in reduction of Klp61F protein level in early embryos. Proteasome mutations restores the level of Klp61F and suppresses the mitotic defects from knockdown of Galla-2 and Klp61F. Taken together, our data suggest that the CGX complex plays a role for maintaining the Klp61F level to regulate the assembly of bipolar spindles.