DIFFERENTIAL ASSOCIATION OF LINKER HISTONES H1 AND H5 WITH TELOMERIC NUCLEOSOMES IN CHICKEN ERYTHROCYTES

Rat liver telomeric DNA is organised into nucleosomes characterised by a shorter and more homogeneous average nucleosomal repeat than bulk c hromatin as shown by Makarov et al. (1). The latter authors were unabl e to detect the association of any linker histone with the telomeric D NA. We have confirmed these observations but show that in sharp contra st chicken erythrocyte telomeric DNA is organised into nucleosomes who se spacing length and heterogeneity are indistinguishable from those o f bulk chromatin. We further show that chicken erythrocyte telomeric c hromatin contains chromatosomes which are preferentially associated wi th histone H1 relative to histone H5. This contrasts with bulk chromat in where histone H5 is the more abundant species. This observation str ongly suggests that telomeric DNA condensed into nucleosome core parti cles has a higher affinity for H1 than H5. We discuss the origin of th e discrimination of the lysine rich histones in terms of DNA sequence preferences, telomere nucleosome preferences and particular constraint s of the higher order chromatin structure of telomeres.