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Translation tubulin

Multiple genes exist for both a- and (3-tubulins. Tubulin isotypes differ primarily at the carboxy-terminus, the region where most post-translational modifications and MAP interactions occur. While most a- and (3-tubulin isotypes are expressed in all tissues, some are expressed preferentially in different tissues. For example, class III and IVa (3-tubulins are neuron-specific (reviewed in [3,14]). It is not known if such examples of tissue-specific... [Pg.125]

Although taxanes bind to p-tubulin promoting microtubule polymerization and stabilization of the spindle complex, they serve to cause a sustained mitotic block at the metaphase/anaphase boundary. This block will occur at a lower concentration than that which is required to increase the microtubule mass (10). However, it is not completely clear how this interaction with microtubules translates into cell death. Morphologic features and the characteristic DNA fragmentation patterns seen in the setting of apoptosis have been documented in tumor cells after therapy with taxanes (10). These observations are accompanied by the phosphorylation of Bcl-2, an anti-apoptotic protein, changing the cellular balance between Bax and Bcl-2 to a status that favors apoptosis (11). [Pg.66]

Fig. 1.52. Model for the control of translation by tubulin. The amount of tubuhn in animal cells is determined partially by the stabrhty of P-tubuhn mRNA, whereby tubuhn itself acts as the regulating signal. Starting from the 5 cap, various stages of the translation of P-tubuhn mRNA, represented as a chain of small circles, is illustrated in the figure. As soon as the N-terminus of the growing P-chain emerges from the ribosome, the a- and P- subunits of tubulin bind to the terminal MREI sequence, upon which an endonuclease becomes activated by a presently unknown mechanism. The degradation of the P-tubulin mRNA then proceeds. Fig. 1.52. Model for the control of translation by tubulin. The amount of tubuhn in animal cells is determined partially by the stabrhty of P-tubuhn mRNA, whereby tubuhn itself acts as the regulating signal. Starting from the 5 cap, various stages of the translation of P-tubuhn mRNA, represented as a chain of small circles, is illustrated in the figure. As soon as the N-terminus of the growing P-chain emerges from the ribosome, the a- and P- subunits of tubulin bind to the terminal MREI sequence, upon which an endonuclease becomes activated by a presently unknown mechanism. The degradation of the P-tubulin mRNA then proceeds.
Fluorescein-labeled proteins are also used to measure the translational mobility of proteins and lipids by the Fluorescence Recovery After Photo-bleaching technique [54-59]. The uniformly labeled fluorescent sample is flashed with an intense light source to bleach a spot, thus producing a concentration gradient. The rate of recovery of fluorescence in that bleached area is measured and used to calculate the diffusion coefficient of the probe dye into the bleached zone. Such diffusion coefficient measurements have been used to determine the association constants of proteins in cells [60], to measure the exchange of tubulin between the cytoplasm and the microtubules [61,62], to study the polymerization-depolymerization process of actin [63-65] and to monitor the changes that occur upon cell maturation [66,67]. [Pg.322]

Epothilones retain significant activity against paclitaxel-selected cell lines that harbor a distinct set of tubulin mutations, and again this could perhaps translate into clinical utility in the treatment of Taxol-resistant tumors. However, any such predictions must be treated with great caution, as the clinical significance of individual resistance mechanisms identified in vitro has not been established. [Pg.8]

On the other hand, it has been suggested, based on immunopre-cipitation reactions, that CCT might interact with a broad range (accounting for 9-15%) of newly synthesized eukaryotic proteins (Feldman and Frydman, 2000 McCallum et al., 2000 Thulasiraman et al., 1999). There is also evidence that some proteins other than actins and tubulins fold via interaction with CCT. These include G -transducin (Farr etal, 1997), cyclinE (Won etal., 1998), and the von Hippel-Landau tumor suppressor protein VHL (Feldman et al., 1999). Moreover, translation in vitro of myosin heavy and light chains has identified an intermediate in the biogenesis of the heavy meromyosin subunit (HMM) of skeletal muscle myosin that contains all three myosin subunits and CCT, from which partially folded HMM can be released in an ATP-dependent reaction. Other as yet unknown cytosolic protein(s) are also apparently required for the completion of the myosin folding reaction (Srikakulam and Winkelmann, 1999). [Pg.80]

Cleveland, D. W., M. W. Kirschner, and N. J. Cowan (1978). Isolation of separate mRNAs for alpha-and beta-tubulin and characterization of the corresponding in vitro translation products. Cell 15,1021-1031. [Pg.99]

Jayanarayan KG, Dey CS. Altered tubulin dynamics, localization and post-translational modifications in sodium arsenite resistant Leishmania donovani in response to paclitaxel, trifluralin and a combination of both and induaion of apoptosis-like cell death. Parasitology 2005 131 215-230. [Pg.7]

Helical symmetry The polymeric proteins of filamentous viruses and the cytoskel-ton possess helical symmetry, in which subunits are related by a translation, as well as a rotational component. Actin, myosin, tubulin and various other fibrous proteins all interact with helical symmetry, which is often called screw symmetry. Screw symmetry, which relates the positions of adjacent subunits, combines a translation along the helix axis with the rotation. Actin forms a two-stranded helix of globular actin subunits. However, important variations in the helix parameters occur (Egehnan et al, 1982). The rise per subunit is relatively constant, but the twist or relative rotation around the helix axis is highly variable. This polymorphic tendency is probably important for the smooth functioning of muscle contraction, which involves considerable force generation. [Pg.139]

Interruptions of post-translational modifications play a major role in the hyperphosphorylation of tau, which lead to structural and conformational changes. Hyperphosphorylation of tau affects its binding to tubulin, leading to destabilization of microtubular network and impairment of microtubule-associated axonal transport. [Pg.493]


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See also in sourсe #XX -- [ Pg.176 ]




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