SUNY at Albany
June 19-23, 2001
Columnar Structure Of Telomeric Chromatin
Telomeres belong to the key functional elements of eukaryotic chromosomes. Like all the other parts of the genome, they exist and function as complexes of DNA with histones and various nonhistone proteins, including specific telomere-binding proteins. Studies of telomeric chromatin have shown on the one hand a lack of nucleosome positioning, and on the other hand a specific nucleosome spacing as revealed by micrococcal nuclease digestion. Based on these properties and on accumulated experimental data, we present a model for a columnar packing of nucleosomes in telomeric chromatin In the columnar model (Fig. 1), the DNA is continuously wound in a parallel manner around the stacked histone octamers and linkers are deformed in the same manner as the deformable part of the nucleosome DNAs.
Figure. 1: Model of columnar packing of telomeric nucleosomes.
Octamer-to-octamer stacking contacts would then cooperatively keep the overall structure, preventing the whole nucleosome array from sliding. The proposed structure offers a relatively condensed arrangement of nucleosomes, which presumably results in a low flexibility of the columnar chromatin fibre. DNA in telomeric chromatin, however, remains relatively accessible for specific telomere-binding proteins. This would contribute to the necessary dynamics of telomeres in their diverse functions..
This work was supported by the Grant Agency of the Czech Republic, Project 301/99/0045, and the Ministry of Education of the Czech Republic, Project MSM 143100008.
Jiri Fajkus (1) and Edward N. Trifonov (2)
CZ-61265 Brno, Czech Republic.