Inducible expression of a cloned heat shock fusion gene in sea urchin embryos.

A fusion gene construct, in which the coding sequence for bacterial chloramphenicol acetyltransferase (CAT; acetyl-CoA: chloramphenicol 3-O-acetyltransferase, EC 2.3.1.28) was placed under the control of the regulatory region of the Drosophila gene encoding the 70-kilodalton heat shock protein [Di Nocera, P.P. & Dawid, I.B. (1983) Proc. Natl. Acad. Sci. USA 80, 7095-7098], was microinjected into the cytoplasm of unfertilized sea urchin eggs. Pluteus-stage embryos developing from the injected eggs were exposed to high temperature conditions that we found would elicit an endogenous sea urchin heat shock response. These embryos express the gene for CAT and, after heat treatment, display 8-10 times more CAT enzyme activity than do extracts from control embryos cultured at normal temperatures. The injected DNA is present in high molecular weight concatenates and, during development, is amplified about 100-fold. Amplified sequences are responsible for all or most of the induced CAT enzyme activity.