Immunochemical detection of chromosomal protein HMG-17 in chromatin subunits

Abstract

Chromosomal protein HMG-17, purified from calf thymus, was 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 [human cervical cancer] 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.