Identification of histone H2b as a heat-shock protein in Drosophila.

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Abstract
Total cell polypeptides synthesized in cultured Drosophila cells under control (25.degree. C) and heat-shock (37.degree. C) conditions were compared in 2 different 2-dimensional polyacrylamide gel electrophoresis systems which, together, resolve polypeptides having a wide range of isoelectric points, including the most basic polypeptides of the cell. The electrophoresis of basic proteins showed that the most prominent basic polypeptide synthesized in heat shock comigrated with histone H2b. This heat-shock polypeptide was identified as histone H2b by 2 criteria: it comigrated with authentic histone H2b in Triton-urea-acetic acid acrylamide gel electrophoresis after solubilization from nuclei with acid; and partial proteolysis peptide maps of the basic heat-shock protein and histone H2b were identical. The synthesis of histone H2b was induced 3-fold in heat shock; synthesis of the other histones was reduced from 2- to 10-fold. The noncoordinate synthesis of histones in Drosophila in heat shock provides an interesting system in which to investigate transcriptional and translational controls of histone synthesis and assembly of histones into chromatin.