Serological detection of homologies of H1o with H5 and H1 histones.

Immunospecifically purified anti-chicken H5 antibodies caused bright staining of mouse liver nuclei in an indirect immunofluorescence assay. Analysis with the fluorescence-activated cell sorter showed that 95% of the nuclei were in the brightest category. Histones extracted from mouse liver nuclei, analyzed by sodium dodecyl sulfate-gel electrophoresis, presented an extra band with the same mobility as chick erythrocyte H5. Electrophoretic blots on nitrocellulose paper were treated with anti-H5 or anti-H1 antibodies and iodinated protein A. The affinity purified anti-H5 bound to chicken H5 and mouse H1o fractions only. Anti-calf H1 bound to calf, chicken, and mouse H1 proteins and to mouse H1o as well. Antibodies to purified subfractions of rat thymus H1 showed binding to both H1 and H1o. The results support the suggestions that H1o bears significant structural homology with H5 and H1.