NUCLEOSOMAL ORGANIZATION OF TELOMERE-SPECIFIC CHROMATIN IN RAT

Rat liver interphase chromosomes have telomeres 20-100 kb in length. M icrococcal nuclease digestion of nuclei cleaves telomeres with a unifo rm 157 bp periodicity, producing soluble particles that sediment in su crose gradients exactly like oligonucleosomes. The monomeric telomere particles comigrate with nucleosome core particles on nucleoprotein an d DNA gels but do not bind H1. DNAase I cleaves telomere nucleoprotein into a series of bands spaced by about 10.4 bp and with the same inte nsity distribution as bands from bulk nucleosomes. Removal of H1 from chromatin alters the sedimentation properties of telomeres in parallel with bulk chromatin. Thus, telomeres of mammals are constructed of cl osely spaced nucleosomes, in contrast with the telomeres of lower euka ryotes, which show no evidence of nucleosomal structure.