DNA sequence-specific binding activity of the heat-shock transcription factor is heat-inducible before the midblastula transition of early Xenopus development.
We have examined the activity of the Xenopus heat-shock transcription factor (HSF) in extracts from stressed and unstressed embryos at various stages of development using DNA mobility shift analysis. A specific interaction between HSF and a synthetic oligonucleotide corresponding to the proximal heat-shock element (HSE) of the Xenopus HSP70B gene was greatly enhanced in heat-shocked embryos compared to controls. HSF binding was inducible at all developmental stages examined including pre-midblastula transition (MBT) stages which are incapable of expressing HSP genes. In time-course experiments with both cleavage and neurula stage embryos, the activation of HSF binding was rapid and transient. Removal of cleavage and neurula stage embryos from heat stress resulted in a rapid loss of binding activity. The molecular mass of HSF, as determined by comparative gel electrophoresis of photoaffinity-labeled factor was 88 x 10(3) in both heat-shocked cleavage and neurula stage embryos. These experiments suggest that maternally derived HSF is stored in pre-MBT embryos in a heat-activatable form and may function in the regulation of heat-shock genes immediately after the MBT.
Ovsenek
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N
Department of Biology, University of Waterloo, Ontario, Canada.
Heikkila
J J
JJ
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001755:Blastocyst / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics*; D006358:Hot Temperature; D008969:Molecular Sequence Data; D008970:Molecular Weight; D014157:Transcription Factors / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology*
D004268:DNA-Binding Proteins; D006360:Heat-Shock Proteins; D014157:Transcription Factors