Abstract
Isolated HeLa cell nucleosomes (core particles) were labeled at the 5'-termini of their DNA with 32P using [gamma-32P]ATP and polynucleotide kne by sequential methylation, depurination, Schiff base formation, and reduction with sodium borhydride. After digestion of the noncrosslinked DNA by DNase I and venom phosphodiesterase, histones were separated by gel electrophoresis and those crosslinked to the 5'-termini were identified by 32P-autoradiography. Histones H3 and H4 occur with equeal frequency as the nearest protein neighbors to the end of the DNA in nucleosomes. Histone arrangements within the core particle compatible with these results are discussed.