Abstract
Localization and local translation of oskar mRNA at the posterior pole of the Drosophila oocyte directs abdominal patterning and germline formation in the embryo. The process requires recruitment and precise regulation of motor proteins to form transport‐competent mRNPs. We show that the posterior‐targeting kinesin‐1 is loaded upon nuclear export of oskar mRNPs, prior to their dynein‐dependent transport from the nurse cells into the oocyte. We demonstrate that kinesin‐1 recruitment requires the DmTropomyosin1‐I/C isoform, an atypical RNA‐binding tropomyosin that binds directly to dimerizing oskar 3′UTRs. Finally, we show that a small but dynamically changing subset of oskar mRNPs gets loaded with inactive kinesin‐1 and that the motor is activated during mid‐oogenesis by the functionalized spliced oskar RNA localization element. This inefficient, dynamic recruitment of Khc decoupled from cargo‐dependent motor activation constitutes an optimized, coordinated mechanism of mRNP transport, by minimizing interference with other cargo‐transport processes and between the cargo‐associated dynein and kinesin‐1.
Highlights
Within cells, organelles, diverse macromolecules and complexes depend on a small set of cytoskeleton-associated motor proteins to achieve their proper distributions
To test whether the loss of kinesin heavy chain (Khc) activity might be the cause of oskar mislocalization in Tm1gs oocytes, we tethered a minimal Khc motor, Khc401 (Sung et al, 2008; Telley et al, 2009), to the MS2-tagged oskar messenger ribonucleoprotein (mRNP)
Tethering of Khc401–MCP to oskMS2 restored the plus-end dominance of oskar mRNP runs (Fig 1D), as well as localization of oskar mRNA (Fig 1E and F), indicating that in Tm1gs mutants a loss of kinesin-1 activity might be the cause of oskar mislocalization
Summary
Organelles, diverse macromolecules and complexes depend on a small set of cytoskeleton-associated motor proteins to achieve their proper distributions. A few LEs, their RNA binding proteins (RBP) and the factors that link them to the mechanoenzyme have been well characterized (Dienstbier et al, 2009; Bullock et al, 2010; Dix et al, 2013; Niedner et al, 2014). In these cases, the entire localization process is driven by a single type of motor. Other mRNAs, such as Xenopus laevis Vg1 (Gagnon et al, 2013) and Drosophila melanogaster oskar (Clark et al, 2007; Zimyanin et al, 2008; Jambor et al, 2014), rely on the coordinated action of multiple motor proteins—cytoplasmic dynein and kinesin-1 and kinesin-2 family members—for their localization within developing oocytes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
