Immunochemical detection of chromosomal protein HMG-17 in chromatin subunits

Chromosomal protein HMG-17, purified from calf thymus, has been used to elicit specific antibodies in rabbits. Specific serological reaction between the antigen and the antisera is demonstrated by solid-phase radioimmunoassay and by competitive inhibition assays. The antisera did not cross-react with histones or other chromosomal HMG proteins. The antisera bound specifically to chromatin subunits isolated from HeLa cells, demonstrating that it may be used to study the in situ organization of this chromosomal protein. Chromatin purified from HeLa nuclei was digested with micrococcal nuclease, and the resulting mono- and oligonucleosomes were fractionated on a sucrose gradient. Analyses of the content of chromosomal proteins HMG-1, HMG-17, and H4 in different size nucleosomal particles, by the solid-phase radioimmunoassay, reveal that the distribution of HMG-17 was the same as that of H4, but different from that of HMG-1.