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Published November 1992 | Published
Journal Article Open

Continuous growth of vimentin filaments in mouse fibroblasts

Abstract

We have investigated the dynamics of intermediate filament assembly in vivo by following the fate of heterologous chicken vimentin subunits expressed under the control of an inducible promoter in transfected mouse fibroblasts. Using RNase protection, metabolic protein pulse-chase and immunofluorescence microscopy, we have examined the fate of newly assembled subunits under physiological conditions in situ. Following induction and subsequent removal of inducer, chicken vimentin mRNA had a half-life of approximately 6 h while both chicken and mouse vimentin protein polymer had long half-lives--roughly equivalent to the cell generation time. Moreover, following deinduction, chicken vimentin immunolocalization progressed from a continuous (8-10 h chase) to a discontinuous (> or = 20 h chase) pattern. The continuous chicken vimentin staining reflects the uniform incorporation of chicken vimentin throughout the endogenous mouse vimentin network while the discontinuous or punctate chicken vimentin staining represents short interspersed segments of assembled chicken vimentin superimposed on the endogenous polymer. This punctate staining pattern of chicken vimentin was present throughout the entire array of intermediate filaments, with no bias toward the perinuclear region. These results are consistent with a continuous growth model of intermediate filament assembly, wherein subunit addition occurs at discrete sites located throughout the cytoskeleton.

Additional Information

© 1992 by Company of Biologists. Received 21 May 1992. Accepted 24 July 1992. The authors thank the other members of the Lazarides laboratory for their critical input and many useful discussions. Special thanks to Dr. Frank Sangiorgi for his RNase protection tutelage and Alexander Kratz (Yale University) for his statistical expertise. We also warmly thank Drs. William Dunphy (Caltech), Sarah Fashena (Yale University), Douglas Fishkind (Worcester Foundation of Experimental Biology), John Ngai (Columbia University) and Barbara Wold (Caltech) for their helpful discussions and comments on the manuscript. This work was supported by grants from the National Institutes of Health (AG 06078A). T.R.C. was supported by a postdoctoral fellowship from the Damon Runyon-Walter Winchell Cancer Research Fund (DRG-990).

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August 20, 2023
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October 24, 2023