Phosphatase-sensitive regulators of microtubule assembly copurify with sea urchin egg microtubules

Brisch, Ellen; Ahrens, Douglas P.; Suprenant, Kathy A.

doi:10.1002/(sici)1097-010x(19990215)283:3<258::aid-jez4>3.0.co;2-u

Cited by 3 publications

(2 citation statements)

References 55 publications

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“…Accordingly, we propose that the MT stabilizing activity of DMAP‐85 is abolished during early stages of embryonic development when most of the MTs are highly dynamic polymers, characterized by the absence of any tubulin modifications associated with stable MTs [49,50]. Similar results have been obtained for other MAPs, including XMAP‐4 [8], p220 [4,51] MAP‐4 [5], EMAP‐115 [52], CP‐60 [19] and EMAP [53]. The phosphorylation of these MAPs correlates with the transition from interphase to mitosis, and it has been associated with the activation of the general mitotic kinases, such as p34 cdc2 [11].…”

Section: Discussionsupporting

confidence: 74%

Microtubule binding of the Drosophila DMAP‐85 protein is regulated by phosphorylation in vitro

et al. 2000

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The phosphorylation of microtubule-associated proteins (MAPs) is thought to be a key factor in the regulation of microtubule (MT) stability. Previously we isolated DMAP-85, a Drosophila MAP shown to be associated with stable MTs. In this work we show that DMAP-85 phosphorylated in cell-free early embryo extracts is released from MTs. MPM-2 antibodies recognize the phosphorylated protein. In vitro, DMAP-85 can be phosphorylated by the mitotic kinase Polo affecting its binding to MTs and creating MPM-2 epitopes on the protein. The results suggest that phosphorylation of DMAP-85 might affect its MT stabilizing activity during early mitotic cycles. ß

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Section: Discussionsupporting

confidence: 74%

Microtubule binding of the Drosophila DMAP‐85 protein is regulated by phosphorylation in vitro

et al. 2000

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“…The rates of microtubule turnover shift dramatically during mitosis (for reviews see Desai and Mitchison, 1997;Cassimeris, 1999), and the 10-fold increase in microtubule catastrophe rates seen in cell-free extracts is dependent on p34 cdc2 (Belmont et al, 1990;Belmont and Mitchison, 1996;Verde et al, 1990). Indeed, p34 cdc2 -cyclin B has been shown to bind and phosphorylate both microtubule-associated protein 4 (Vandré et al, 1991;Ookata et al, 1995) and p77 echinoderm microtubule-associated protein (Brisch et al, 1996), and MAP kinase family members have also been implicated in the regulation of microtubule dynamic instability (Gotoh et al, 1991;Brisch et al, 1999). Phosphorylation lowers the affinity of MAPs for the microtubule, resulting in increasing catastrophe rates (McNally, 1996).…”

Section: Delivery Of the Cleavage Stimulus And The Timing Of Cytokinesismentioning

confidence: 99%

Parameters That Specify the Timing of Cytokinesis

Shuster

Burgess

1999

The Journal of Cell Biology

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One model for the timing of cytokinesis is based on findings that p34cdc2 can phosphorylate myosin regulatory light chain (LC20) on inhibitory sites (serines 1 and 2) in vitro (Satterwhite, L.L., M.H. Lohka, K.L. Wilson, T.Y. Scherson, L.J. Cisek, J.L. Corden, and T.D. Pollard. 1992. J. Cell Biol. 118:595–605), and this inhibition is proposed to delay cytokinesis until p34cdc2 activity falls at anaphase. We have characterized previously several kinase activities associated with the isolated cortical cytoskeleton of dividing sea urchin embryos (Walker, G.R., C.B. Shuster, and D.R. Burgess. 1997. J. Cell Sci. 110:1373–1386). Among these kinases and substrates is p34cdc2 and LC20. In comparison with whole cell activity, cortical H1 kinase activity is delayed, with maximum levels in cortices prepared from late anaphase/telophase embryos. To determine whether cortical-associated p34cdc2 influences cortical myosin II activity during cytokinesis, we labeled eggs in vivo with [32P]orthophosphate, prepared cortices, and mapped LC20 phosphorylation through the first cell division. We found no evidence of serine 1,2 phosphorylation at any time during mitosis on LC20 from cortically associated myosin. Instead, we observed a sharp rise in serine 19 phosphorylation during anaphase and telophase, consistent with an activating phosphorylation by myosin light chain kinase. However, serine 1,2 phosphorylation was detected on light chains from detergent-soluble myosin II. Furthermore, cells arrested in mitosis by microinjection of nondegradable cyclin B could be induced to form cleavage furrows if the spindle poles were physically placed in close proximity to the cortex. These results suggest that factors independent of myosin II inactivation, such as the delivery of the cleavage stimulus to the cortex, determine the timing of cytokinesis.

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Focusing-in on microtubules

Amos

2000

Current Opinion in Structural Biology

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Phosphatase-sensitive regulators of microtubule assembly copurify with sea urchin egg microtubules

Cited by 3 publications

References 55 publications

Microtubule binding of the Drosophila DMAP‐85 protein is regulated by phosphorylation in vitro

Microtubule binding of the Drosophila DMAP‐85 protein is regulated by phosphorylation in vitro

Parameters That Specify the Timing of Cytokinesis

Focusing-in on microtubules

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