Constitutive expression of a somatic heat-inducible hsp70 gene during amphibian oogenesis

• Published in: Development (Cambridge) Vol. 119; no. 3; pp. 921 - 932
• Main Authors: BILLOUD, B, RODRIGUEZ-MARTIN, M.-L, BERARD, L, MOREAU, N, ANGELIER, N
• Format: Journal Article
• Language: English
• Published: Cambridge The Company of Biologists Limited 01.11.1993; Company of Biologists
• Subjects: Amino Acid Sequence; Animals; Base Sequence; Biological and medical sciences; Blotting, Northern; Blotting, Western; Freshwater; Fundamental and applied biological sciences. Psychology; Gene Expression - physiology; Heat-Shock Proteins - genetics; In Situ Hybridization; Molecular Sequence Data; Non mammalian vertebrate reproduction; Oogenesis - genetics; Pleurodeles - genetics; Pleurodeles waltlii; Transcription, Genetic - genetics; Vertebrates: reproduction; Oogenesis; Reproduction; Vertebrata; Pleurodeles waltlii; Transcription; Caudata; Heat shock protein; Amphibia; Chromosome; Gene expression
• ISSN: 0950-1991; 1477-9129
• DOI: 10.1242/dev.119.3.921

We isolated and characterized a sequence coding for heat-shock protein 70 (HSP70) of the amphibian Pleurodeles waltl. Results from S1 nuclease protection assays led us to conclude that an hsp70 gene, strictly inducible in somatic cells during heat shock, is constitutively active during oogenesis. By quantitative northern and western blot analysis, we showed that both hsp70 mRNA and HSP70-related protein levels increased in oocytes from stage II to stage VI under physiological conditions. Furthermore, by in situ hybridization to the nascent transcripts of lampbrush chromosome loops, we provided evidence for a clear-cut relationship between this increase in hsp70 mRNA and transcriptional activity during the lampbrush stage of oogenesis. These results strongly suggest that hsp70 genes are actively transcribed throughout oogenesis. HSP70-related proteins localized in the cytoplasm of young oocytes are progressively transferred to the nucleus in the course of oogenesis and preferentially accumulated in the nuclei of some stage VI oocytes.