Transcription of a Drosophila heat shock gene is heat-induced in Xenopus oocytes.

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Abstract
Xenopus cells, like many other eukaryotic cells, respond to heat treatments by increasing the rate of synthesis of a few characteristic proteins, the heat shock proteins. Because of the generality of this response, it seemed possible to examine the expression of isolated heat shock genes in a heterologous system. Phage 122 DNA, containing 2 identical genes coding for the Drosophila 70,000-dalton heatshock protein (hsp70 genes), was microinjected into Xenopus oocyte nuclei. The Drosophila hsp70 genes are transcribed efficiently in heat-treated oocytes (35-37.degree. C) to give RNA of the correct size and sequence content. Transcription is sensitive to low levels of .alpha.-amanitin and therefore is carried out by RNA polymerase II. At normal temperatures (20-28.degree. C) essentially no Drosophila-specific RNA is formed. The isolated insert fragment of phage 122 also gives RNA of correct length in heat-treated oocytes which hybridizes to the coding segment of Drosophila hsp70 genes only. At normal temperatures, its rate of transcription is variable and only RNA heterogeneous in size is formed.