Protein component from Drosophila larval nuclei showing sequence specificity for a short region near a major heat-shock protein gene.

Using a nitrocellulose filter binding assay we have detected a protein component in extracts prepared from the nuclei of D. melanogaster third instar larvae which shows sequence-specific binding to a short region on a cloned D. melanogaster DNA segment containing a copy of the major heat-shock protein gene. The specificity of binding was confirmed by direct visualization of the protein DNA complexes in the electron microscope. Protein blotting experiments demonstrated that three polypeptides in the extract were capable of such sequence-specific binding. The protein binding site detected in this cloned sequence lies 800-1000 bp upstream from the presumptive transcription start.