EXPRESSION AND POSTTRANSLATIONAL MODIFICATION OF CLASS-III BETA-TUBULIN DURING NEURONAL DIFFERENTIATION OF P19 EMBRYONAL CARCINOMA-CELLS

We have used a combination of immunofluorescence microscopy, northern blotting, ELISA, and isoelectric focusing to characterize the expressi on of neuronal Class III beta-tubulin in P19 embryonal carcinoma cells induced to differentiate along a neuronal pathway by retinoic acid. F ollowing 48 h differentiation, beta-III tubulin mRNA is evident and be ta-III tubulin appears in the mitotic spindle of neuroblasts. Neurite outgrowth is obvious by day 3, and beta-III tubulin protein and mRNA l evels increase concurrently until approximately day 7, when beta-III m RNA levels begin to decrease while protein levels remain high, In addi tion, increasingly acidic beta-III tubulin isoforms appear during neur onal differentiation. The expression of these isoelectric variants occ urs concomitant with a temporal increase in the levels of beta-III tub ulin present in the colchicine-stable microtubules. These results impl icate posttranslational modifications of beta-III tubulin in the incre ased microtubule. stability noted in differentiating P19 neurons. (C) 1996 Wiley-Liss, Inc.