Journal Article

Inhibition of Proteasome by MG-132 Treatment Causes Extra Phragmoplast Formation and Cortical Microtubule Disorganization during M/G<sub>1</sub> Transition in Synchronized Tobacco Cells

Masayoshi Oka, Yuki Yanagawa, Tetsuhiro Asada, Arata Yoneda, Seiichiro Hasezawa, Takahide Sato and Hiroki Nakagawa

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 11, pages 1623-1632
Published in print November 2004 | ISSN: 0032-0781
Published online November 2004 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pch183
Inhibition of Proteasome by MG-132 Treatment Causes Extra Phragmoplast Formation and Cortical Microtubule Disorganization during M/G1 Transition in Synchronized Tobacco Cells

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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The 26S proteasome plays essential roles in cell cycle progression in various types of cell. We previously reported that the inhibition of 26S proteasome activities by a proteasome inhibitor, MG-132, exclusively caused cell cycle arrest in synchronized tobacco BY-2 cells. Here we report a further observation of 26S proteasome involvement during M/G1 transition utilizing a transgenetic BY-2 cell line that stably expresses a GFP–α-tubulin fusion protein (BY-GT16). Interestingly, MG-132 treatment caused the arrest of cell cycle progression prior to entering the G1 phase. Indeed, phragmoplast-like structures were formed and cortical microtubules were not organized after the collapse of the original phragmoplasts. Additionally, actin microfilaments showed irregular rearrangements when further incubated with MG-132 and as the phragmoplast-like structures developed. Since these phragmoplast-like structures had a similar configuration and ability to form cell plates to that of the original phragmoplasts, we designated these phragmoplast-like structures as extra phragmoplasts. Furthermore, we showed that a tobacco kinesin-related polypeptide of 125 kDa (TKRP125) localized in the extra phragmoplasts and that its protein level remained unchanged during MG-132 treatment. We propose that TKRP125 might be one of the possible targets of the ubiquitin-proteasome degradation pathway during M/G1 transition.

Keywords: Keywords: Cell cycle — M/G1 transition — Phragmoplast — 26S Proteasome — TKRP125 — Tobacco BY-GT16.; Abbreviations: APC, anaphase-promoting complex; BY-GT16, BY-2 cells expressing GFP-tubulin fusion protein clone 16; CLSM, confocal laser scanning microscopy; GFP, green fluorescent protein; KRP, kinesin-related protein; MF, actin microfilament; MT, microtubule; TKRP125, tobacco kinesin-related polypeptide of 125 kDa.

Journal Article.  6070 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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