RT Journal Article SR Electronic T1 Mechanisms of Kinesin-1 activation by Ensconsin/MAP7 in vivo JF bioRxiv FD Cold Spring Harbor Laboratory SP 325035 DO 10.1101/325035 A1 Mathieu Métivier A1 Brigette Y. Monroy A1 Emmanuel Gallaud A1 Renaud Caous A1 Aude Pascal A1 Laurent Richard-Parpaillon A1 Antoine Guichet A1 Kassandra M. Ori-McKenney A1 Régis Giet YR 2018 UL http://biorxiv.org/content/early/2018/07/27/325035.abstract AB Centrosome separation in Drosophila larval neuroblasts and asymmetric transport of embryonic determinants in oocytes are both microtubule-dependent processes that require Kinesin-1 activation by Ensconsin/microtubule-associated protein 7 (MAP7). However, the molecular mechanism used by Ensconsin to activate Kinesin-1 remains elusive. Ensconsin/ MAP7 contains an N-terminal microtubule-binding domain (MBD) and a C-terminal Kinesin-binding domain (KBD). Using rescue experiments in live flies, we show that KBD expression alone is sufficient to fully rescue Ensconsin-dependent centrosome separation defects, but not the fast oocyte streaming and the localization patterns of Staufen and Gurken proteins. Interestingly, we show here for the first time that KBD binds and stimulates Kinesin-1 binding to Mts in vivo and in vitro. We propose that the KBD/Kinesin-1 motor represents a minimal activation module that stimulates Kinesin-1 binding to Mts. Addition of the MBD, present in the full length Ensconsin allows this activation to occur directly on the Mt. Our data also suggest that in a very large cell with a complex microtubule network, but not in smaller cells, this dual activation by Ensconsin is essential for optimal Kinesin-1 targeting to the microtubule cytoskeleton.