Dataset Information

Visualizing microtubule structural transitions and interactions with associated proteins.

ABSTRACT: Microtubules (MTs) have been the subject of cryo-electron microscopy (cryo-EM) studies since the birth of this technique. Although MTs pose some unique challenges, having to do with the presence of a MT seam, lattice variability and disorder, MT cryo-EM reconstructions are steadily improving in resolution and providing exciting new insights into MT structure and function. Recent work has lead to the atomic-detail visualization of lateral contacts between tubulin subunits and the conformational changes that give rise to strain in the MT lattice accompanying GTP hydrolysis. Cryo-EM has also been invaluable in describing the interactions between MTs and MT associated proteins (MAPs), which function to regulate MT dynamic instability, move cargoes, or contribute to other MT cellular processes.

SUBMITTER: Nogales E

PROVIDER: S-EPMC4834239 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Visualizing microtubule structural transitions and interactions with associated proteins.

Nogales Eva E Zhang Rui R

Current opinion in structural biology 20160121

Microtubules (MTs) have been the subject of cryo-electron microscopy (cryo-EM) studies since the birth of this technique. Although MTs pose some unique challenges, having to do with the presence of a MT seam, lattice variability and disorder, MT cryo-EM reconstructions are steadily improving in resolution and providing exciting new insights into MT structure and function. Recent work has lead to the atomic-detail visualization of lateral contacts between tubulin subunits and the conformational c ...[more]

PMID: 26803284

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Project description:Factor quinolinone inhibitors (FQIs), a first-in-class set of small molecule inhibitors targeted to the transcription factor LSF (TFCP2), exhibit promising cancer chemotherapeutic properties. FQI1, the initial lead compound identified, unexpectedly induced a concentration-dependent delay in mitotic progression. Here, we show that FQI1 can rapidly and reversibly lead to mitotic arrest, even when added directly to mitotic cells, implying that FQI1-mediated mitotic defects are not transcriptionally based. Furthermore, treatment with FQIs resulted in a striking, concentration-dependent diminishment of spindle microtubules, accompanied by a concentration-dependent increase in multi-aster formation. Aberrant γ-tubulin localization was also observed. These phenotypes suggest that perturbation of spindle microtubules is the primary event leading to the mitotic delays upon FQI1 treatment. Previously, FQIs were shown to specifically inhibit not only LSF DNA-binding activity, which requires LSF oligomerization to tetramers, but also other specific LSF-protein interactions. Other transcription factors participate in mitosis through non-transcriptional means, and we recently reported that LSF directly binds α-tubulin and is present in purified cellular tubulin preparations. Consistent with a microtubule role for LSF, here we show that LSF enhanced the rate of tubulin polymerization in vitro, and FQI1 inhibited such polymerization. To probe whether the FQI1-mediated spindle abnormalities could result from inhibition of mitotic LSF-protein interactions, mass spectrometry was performed using as bait an inducible, tagged form of LSF that is biotinylated by endogenous enzymes. The global proteomics analysis yielded expected associations for a transcription factor, notably with RNA processing machinery, but also to nontranscriptional components. In particular, and consistent with spindle disruption due to FQI treatment, mitotic, FQI1-sensitive interactions were identified between the biotinylated LSF and microtubule-associated proteins that regulate spindle assembly, positioning, and dynamics, as well as centrosome-associated proteins. Probing the mitotic LSF interactome using small molecule inhibitors therefore supported a non-transcriptional role for LSF in mediating progression through mitosis.

Dataset Information

Visualizing microtubule structural transitions and interactions with associated proteins.

Publications

Visualizing microtubule structural transitions and interactions with associated proteins.

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