A microtubule interactome: complexes with roles in cell cycle and mitosis.

The microtubule (MT) cytoskeleton is required for many aspects of cell function, including the transport of intracellular materials, the maintenance of cell polarity, and the regulation of mitosis. These functions are coordinated by MT-associated proteins (MAPs), which work in concert with each other, binding MTs and altering their properties. We have used a MT cosedimentation assay, combined with 1D and 2D PAGE and mass spectrometry, to identify over 250 MAPs from early Drosophila embryos.

Akt regulates centrosome migration and spindle orientation in the early Drosophila melanogaster embryo.

Correct positioning and morphology of the mitotic spindle is achieved through regulating the interaction between microtubules (MTs) and cortical actin. Here we find that, in the Drosophila melanogaster early embryo, reduced levels of the protein kinase Akt result in incomplete centrosome migration around cortical nuclei, bent mitotic spindles, and loss of nuclei into the interior of the embryo. We show that Akt is enriched at the embryonic cortex and is required for phosphorylation of the glycogen synthase kinase-3beta homologue Zeste-white 3 kinase (Zw3) and for the cortical localizations of the adenomatosis polyposis coli (APC)-related protein APC2/E-APC and the MT + Tip protein EB1.

Inscuteable mRNA localization is dynein-dependent and regulates apicobasal polarity and spindle length in Drosophila neuroblasts.

Drosophila neuroblasts undergo asymmetric divisions along the apicobasal axis to produce two daughter cells of unequal size and different developmental fate. Inscuteable (Insc) protein functions as part of an apically localized complex to coordinate orientation of the mitotic spindle and basal sorting of cell fate determinants. insc mRNA transcripts also localize apically in neuroblasts, yet the mechanism underpinning this process and its developmental significance are unknown.

Differential cytoplasmic mRNA localisation adjusts pair-rule transcription factor activity to cytoarchitecture in dipteran evolution.

Establishment of segmental pattern in the Drosophila syncytial blastoderm embryo depends on pair-rule transcriptional regulators. mRNA transcripts of pair-rule genes localise to the apical cytoplasm of the blastoderm via a selective dynein-based transport system and signals within their 3'-untranslated regions. However, the functional and evolutionary significance of this process remains unknown.