IDENTIFICATION OF MEMBERS OF THE HSP30 SMALL HEAT-SHOCK PROTEIN FAMILY AND CHARACTERIZATION OF THEIR DEVELOPMENTAL REGULATION IN HEAT-SHOCKED XENOPUS-LAEVIS EMBRYOS

In the present study we have characterized the synthesis of members of the HSP30 family during Xenopus laevis development using a polyclonal antipeptide antibody derived from the carboxyl end of HSP30C. Two-dim ensional PAGE/immunoblot analysis was unable to detect any heat-induci ble small HSPs in cleavage, blastula, gastrula, or neurula stage embry os. However, heat-inducible accumulation of a single protein was first detectable in early tailbud embryos with an additional 5 HSPs at the late tailbud stage and a total of 13 small HSPs al the early tadpole s tage. In the Xenopus A6 kidney epithelial cell line, a total of eight heat-inducible small HSPs were detected by this antibody. Comparison o f the pattern of protein synthesis in embryos and somatic cells reveal ed a number of common and unique heat inducible proteins in Xenopus em bryos and cultured kidney epithelial cells. To specifically identify t he protein product of the HSP30C gene, we made a chimeric gene constru ct with the Xenopus HSP30C coding sequence under the control of a cons titutive promoter. This construct was microinjected into fertilized eg gs and resulted in the premature and constitutive synthesis of the HSP 30C protein in gastrula stage embryos. Through a series of mixing expe riments, we were able to specifically identify the protein encoded by the HSP30C gene in embryos and somatic cells and to conclude that HSP3 0C synthesis was first heat-inducible at the early tailbud stage of de velopment. The differential pattern of heat-inducible accumulation of members of the HSP30 family during Xenopus development suggests that t hese proteins may have distinct functions at specific embryonic stages during a stress response. (C) 1995 Wiley-Liss, Inc.