Molecular cloning of a cDNA encoding the nucleosome core histone H3 from Dictyostelium discoideum by genetic screening in yeast.

The one-hybrid method for genetic screening in yeast was used to search a Dictyostelium discoideum cDNA library for DNA-binding proteins that interact with the C-module of the Dictyostelium repetitive element. The C-module was formerly shown to contain two high affinity, sequence-specific binding sites for a nuclear protein factor of unknown function (CMBF). The bait DNA sequence was bound in vivo by a cDNA-encoded protein whose derived amino acid sequence showed high homology to nucleosome core histone H3, but not to partially available CMBF sequences. The D. discoideum histone H3 homolog is encoded by a single gene and shows significant sequence variation at the amino terminus of the protein, including a triple-serine insertion not found in any other histone H3.