INSCUTEABLE AND STAUFEN MEDIATE ASYMMETRIC LOCALIZATION AND SEGREGATION OF PROSPERO RNA DURING DROSOPHILA NEUROBLAST CELL DIVISIONS

When neuroblasts divide, inscuteable acts to coordinate protein locali zation and mitotic spindle orientation, ensuring that asymmetrically l ocalized determinants like Prospero partition into one progeny. staufe n encodes a dsRNA-binding protein implicated in mRNA transport in oocy tes. We demonstrate that prospero RNA is also asymmetrically localized and partitioned during neuroblast cell divisions, a process requiring both inscuteable and staufen. Inscuteable and Staufen interact and co localize with prospero RNA on the apical cortex of interphase neurobla sts. Staufen binds prospero RNA in its 3'UTR. Our findings suggest tha t Inscuteable nucleates an apical complex and is required for protein localization, spindle orientation, and RNA localization. Stau, as one component of this complex, is required only for RNA localization. Henc e staufen also acts zygotically, downstream of inscuteable, to effect aspects of neuroblast asymmetry.