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First published online 2 November 2004
doi: 10.1242/jcs.01515

This Article Figures Only Full Text Full Text (PDF) Supplementary Material All Versions of this Article: jcs.01515v1 117/24/5937    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Lowell, J. E. Articles by Cross, G. A. M. Search for Related Content PubMed PubMed Citation Articles by Lowell, J. E. Articles by Cross, G. A. M.

A variant histone H3 is enriched at telomeres in Trypanosoma brucei

Laboratory of Molecular Parasitology, The Rockefeller University, 1230 York Avenue, New York, NY 10021, USA

^* Author for correspondence (e-mail: george.cross{at}rockefeller.edu)

Accepted 31 August 2004

Variant histones play critical roles in transcriptional activation and repression, DNA repair and chromosome segregation. We have identified HTV, a single-copy gene in Trypanosoma brucei encoding a variant form of histone H3 (H3V). H3V is present at discrete nuclear foci that shift over the course of the cell cycle and associate with the mitotic spindle, a pattern of localization reminiscent of that described previously for both mini-chromosomes and telomeres. By combining fluorescence in situ hybridization with indirect immunofluorescence, we confirmed that the H3V foci overlap with a 177-bp repetitive sequence element found predominantly in mini-chromosomes, as well as with the TTAGGG repeats that compose telomeres. Chromatin immunoprecipitation studies, however, reveal that only the telomeric repeat DNA is substantially enriched with H3V. HTV is not essential for viability, mini-chromosome segregation, telomere maintenance or transcriptional silencing at the telomere-proximal expression sites from which bloodstream-form T. brucei controls antigenic variation. We propose that H3V represents a novel class of histone H3 variant, a finding that has evolutionary implications.

Key words: Histone H3 variant, CenH3, Telomere, Trypanosoma brucei

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