DETECTION OF HEAT-SHOCK ELEMENT-BINDING ACTIVITIES BY GEL SHIFT ASSAYDURING MOUSE PREIMPLANTATION DEVELOPMENT

Heat shock gene expression is regulated by highly conserved sequence e lements (HSE for ''heat shock elements''). Some of heat shock genes di splay an atypical expression during preimplantation mouse development. We have examined the profile of HSE-binding activities (HSE-BA) in ma tured ovulated oocytes and during the preimplantation development by g el shift assay and quantified the data by PhosphorImager. In each of o ur experiments, the F9 embryonal carcinoma cell line that contains bot h constitutive and heat-induced activity has been used as a control. W e determine the number of oocytes or embryos required to get reproduci ble signals and accurate quantification by PhosphorImager. Oocytes, on e-cell, and two-cell embryos respond to heat shock by inducing a stron g HSE-BA. At the four-cell stage, no HSE-BA can be induced by heat sho ck, which suggests that noninducibility of heat shock genes at this st age (when the general mechanism of transcription is well established) might result from a defect in HSF or in the mechanism of HSF activatio n. A progressive reappearance of the ability to induce HSE-BA by stres s is observed between the eight-cell stage and the blastocyst stage, a nd this parallels the appearance of heat shock gene inducibility. Matu red ovulated oocytes and the first cleavage stages of embryos do not c ontain any HSE-BA at normal temperature but we observed a HSE-BA at no rmal temperature at the morula stage, which is increased at the blasto cyst stage. These data, which, to our knowledge, for the first time de scribe the profile of a DNA-binding activity during the mouse preimpla ntation development, could serve as a basis for the study of other tra nscription factors during early embryogenesis. (C) 1994 Academic Press , Inc.