Do Xenopus oocytes have a heat shock response?

Area of Science:

• Cell Biology
• Molecular Biology
• Developmental Biology

Background:

• Previous studies suggested Xenopus oocytes uniquely induce heat shock protein 70 (hsp70) translation upon heat shock.
• Understanding the regulation of inactive mRNA translation is crucial in cell biology.

Purpose of the Study:

• To re-examine the heat shock response in Xenopus oocytes.
• To investigate the potential for using this response to study mRNA translation regulation.

Main Methods:

• Analysis of [35S]methionine-labeled proteins synthesized by defolliculated Xenopus oocytes and unfertilized eggs at ambient and heat shock temperatures.
• Comparison of oocyte response with that of surrounding follicle cells and fibroblasts.

Main Results:

• No evidence of induced hsp70 synthesis in heat-shocked, defolliculated Xenopus oocytes or unfertilized eggs.
• Defolliculated oocytes exhibited thermotolerance in vitro.
• Constitutive synthesis of a 70-kDa protein, part of the hsp70 complex, was observed in oocytes.
• Fibroblasts and follicle cells displayed a classic heat shock response at the transcriptional level.
• hsp70 synthesized by follicle cells was not transported into oocytes.

Conclusions:

• Xenopus oocytes do not exhibit the canonical heat shock protein 70 induction upon heat stress.
• Oocytes may represent a unique exception to the generally conserved heat shock response in eukaryotes.
• The regulation of protein synthesis in oocytes under stress differs significantly from somatic cells.