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Published September 15, 1983 | Published
Journal Article Open

Synthesis and post-translational assembly of intermediate filaments in avian erythroid cells: Vimentin assembly limits the rate of synemin assembly


The assembly of vimentin intermediate filaments and the high molecular weight filament crosslinking protein, synemin, was studied in erythroid cells from 10-day chicken embryos. Pulse labeling studies show that newly synthesized vimentin is present both in a Triton X-100-insoluble form and in a soluble form. The incorporation of labeled vimentin into the insoluble fraction increases linearly with time, while the soluble pool of labeled vimentin saturates quickly. In contrast, synemin accumulates rapidly in the Triton X-100-soluble fraction and begins to accumulate in the insoluble fraction only after a considerable lag of time. Pulse-chase studies reveal that the detergent-soluble pools of both vimentin and synemin contain precursors for their post-translational assembly into detergent-insoluble filaments and that the half-life of soluble synemin is about twice as long as that of soluble vimentin. Immunoprecipitation of solubilized filaments with synemin antiserum precipitates vimentin with synemin. On the other hand, soluble vimentin does not coimmunoprecipitate with soluble synemin. These results suggest that, in the assembly of vimentin and synemin into intermediate filaments, vimentin filament elongation generates synemin binding sites, and thus the rate of vimentin filament elongation limits the rate of synemin assembly.

Additional Information

© 1983 by the National Academy of Sciences. Communicated by Edward B. Lewis, June 3, 1983. We thank John Ngai and Drs. W. James Nelson, Merrill B. Hille, Bruce L. Granger, and Ingrid Blikstad for comments on the manuscript. This work was supported by grants from the National Institutes of Health, the National Science Foundation, and the Muscular Dystrophy Association of America. R.T.M. was also supported by postdoctoral fellowships from the National Institutes of Health and the American Cancer Society. E.L. is a recipient of a Research Career Development Award from the National Institutes of Health. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

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