ARTICLE

SYNTHESIS AND STORAGE OF MICROTUBULE PROTEINS BY SEA URCHIN EMBRYOS

Rudolf A. Raff ¹, Gerald Greenhouse ¹, Kenneth W. Gross ¹, and Paul R. Gross ¹

¹ From the Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139.

Dr. Raff's present address is the Department of Zoology, Indiana University, Bloomington, Indiana 47401

Studies employing colchicine binding, precipitation with vinblastine sulfate, and acrylamide gel electrophoresis confirm earlier proposals that Arbacia punctulata and Lytechinus pictus eggs and embryos contain a store of microtubule proteins. Treatment of 150,000 g supernatants from sea urchin homogenates with vinblastine sulfate precipitates about 5% of the total soluble protein, and 75% of the colchicine-binding activity. Electrophoretic examination of the precipitate reveals two very prominent bands. These have migration rates identical to those of the A and B microtubule proteins of cilia. These proteins can be made radioactive at the 16 cell stage and at hatching by pulse labeling with tritiated amino acids. By labeling for 1 hr with leucine-³H in early cleavage, then culturing embryos in the presence of unlabeled leucine, removal of newly synthesized microtubule proteins from the soluble pool can be demonstrated. Incorporation of labeled amino acids into microtubule proteins is not affected by culturing embryos continuously in 20 µg/ml of actinomycin D. Microtubule proteins appear, therefore, to be synthesized on "maternal" messenger RNA. This provides the first protein encoded by stored or "masked" mRNA in sea urchin embryos to be identified.

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• Norrander, J., Linck, R., Stephens, R. (1995). Transcriptional control of tektin A mRNA correlates with cilia development and length determination during sea urchin embryogenesis. Development 121: 1615-1623 [Abstract]  
• Suprenant, K., Dean, K, McKee, J, Hake, S (1993). EMAP, an echinoderm microtubule-associated protein found in microtubule-ribosome complexes. J. Cell Sci. 104: 445-450 [Abstract]  
• Harlow, P, Nemer, M (1987). Coordinate and selective beta-tubulin gene expression associated with cilium formation in sea urchin embryos.. Genes Dev. 1: 1293-1304 [Abstract]  
• Davidson, E., Hough-Evans, B., Britten, R. (1982). Molecular biology of the sea urchin embryo. Science 217: 17-26 [Abstract]  

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