Nucleosomal organization of telomere-specific chromatin in rat

Abstract

Rat liver interphase chromosomes have telomeres 20-100 kb in length. Micrococcal nuclease digestion of nuclei cleaves telomeres with a uniform 157 bp periodicity, producing soluble particles that sediment in sucrose gradients exactly like oligonucleosomes. The monomeric telomere particles comigrate with nucleosome core particles on nucleoprotein and 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 intensity 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 closely spaced nucleosomes, in contrast with the telomeres of lower eukaryotes, which show no evidence of nucleosomal structure.

Expression of telomerase in normal and malignant rat hepatic epithelia

“…Because of its remarkable regenerative capacity the rat liver has proven to be an excellent model for studies of cell proliferation and carcinogenesis (Cayama et al, 1978;Kaufmann et al, 1981). In spite of an extensive literature on hepatocarcinogenesis, there are few reports on telomeres and telomerase activity in normal rat liver and liver tumors (Makarov et al, 1993;Yoshimi et al, 1996). To determine whether altered expression of telomerase might play a role in rat hepatocarcinogenesis, we characterized telomerase activity in quiescent and regenerating liver, isolated hepatocytes, cultured hepatic epithelial stem-like cells from normal liver, and in immortal and tumorigenic derivatives of these cells.…”

Unusual chromatin in human telomeres.

“…A recent analysis of rat telomeres has suggested that mammalian telomeres are packaged in normal nucleosomal arrays (39). How 16 h to remove all traces of formaldehyde.…”

Telomeres at a glance

“…In contrast with yeast telomeres, which lack histones (Wright et al, 1992), mammalian telomeres are nucleosomal (Makarov et al, 1993;Lejnine et al, 1995) and their chromatin is enriched with repressive histone marks, including H3K9me3 and H4K20me3 (me3 represents trimethylation), and the heterochromatinspecific factors chromobox homolog (CBX) 1, 3 and 5 (García-Cao et al, 2004;Gonzalo et al, 2006). Depletion of these heterochromatic marks correlates with remarkable elongation of telomeres (Marión and Blasco, 2010;Marión et al, 2011;Varela et al, 2011).…”