FOLDING OF CHROMATIN IN THE PRESENCE OF HETEROGENEOUS HISTONE H1 BINDING TO NUCLEOSOMES

We have reconstituted oligonucleosome complexes containing histone Hi starting from a synthetic DNA template, consisting of 12 tandemly arra nged 208-base pair fragments of the 5 S rRNA gene, purified HeLa histo ne octamers, and histone H1. A ratio of histone H1 per histone octamer used in the reconstitution (0.8-0.9 mol of histone H1/mol of histone octamer) similar to that observed in vivo was used. The reconstituted chromatin complexes exhibit a salt-dependent folding, which is almost indistinguishable from that exhibited by chromatin fragments obtained from nuclease digestion of native chromatin, The folding of this recon stituted chromatin complex seems to be rather independent of the symme trical or asymmetrical position occupied by Hi in the individual nucle osomes. Binding of histone H1 to the oligonucleosome complexes, under the stoichiometric binding conditions used, had no inhibitory effect o n the transcriptional potential of these complexes.