HEAT-SHOCK PROTEIN GENE-EXPRESSION DURING XENOPUS DEVELOPMENT

Stress-induced heat shock protein gene expression is developmentally r egulated during early embryogenesis of the frog, Xenopus laevis. For e xample, a number of heat shock protein genes, such as hsp70, hsp90, an d ubiquitin are not heat-inducible until after the midblastula stage o f embryogenesis. Furthermore, the family of small heat shock protein g enes, hsp30, are differentially expressed after the midblastula stage as well as being regulated at the level of mRNA stability. Many of the se stress proteins are also synthesized constitutively during oogenesi s and embryogenesis during which they may act as molecular chaperones as well as being involved in sequestering proteins in an inactive stat e until required by the developing embryo. Furthermore the induction o f these stress protein genes has been correlated with enhanced thermor esistance. During stressful conditions heat shock proteins probably pr event aggregation or misfolding of damaged proteins within the embryo.