Biosynthesis and characterization of heat shock proteins in Chironomus tentans salivary glands.

The protein synthesis response of Chironomus tentans salivary glands to a heat shock was analyzed by means of [3H]leucine pulse labeling, sodium dodecyl sulfate - polyacrylamide slab gels, and fluorography. Seven new cytoplasmic polypeptides with relative masses (Mr) of 90 000, 76 000, 73 000, 68 000, 28 000, 25 000, and 22 000 are synthesized in response to a 39 degrees C heat shock (HS) while the synthesis of most of the normal proteins is reduced. The major HS-induced protein is the 68 000 species. The length of the heat treatment does not modify markedly the pattern of induced proteins but the temperature has an effect: while the responses at 37 and 39 degrees C are similar, two HS-induced polypeptides (Mr 90 000 and 76 000) are not seen after a treatment at 41 degrees C. Kinetic studies of the response show an asynchrony in the appearance of the various HS proteins indicating that their individual rates of synthesis differ or that their induction is not fully coordinated. No significant differences were found between the protein patterns of a mitochondria-rich cytoplasmic zone obtained by microdissection and the whole cytoplasm, but two heat-induced proteins are present in the microdissected nuclei: a 68 000 polypeptide, comigrating with the major cytoplasmic one, and a 34 000 protein, almost exclusively seen in the nucleus.