Research

Repressive and non-repressive chromatin at native telomeres in Saccharomyces cerevisiae

Esther R Loney¹ , Peter W Inglis² , Sarah Sharp³ , Fiona E Pryde⁴ , Nicholas A Kent⁵ , Jane Mellor⁶ and Edward J Louis³

¹  Department of Oncology, University of Western Ontario, Ontario, Canada

²  Embrapa Recursos Geneticos e Biotecnologia, Parque Estacao Biologica, Brasilia-DF, CEP 70770900, CP, 02372, Brazil

³  Institute of Genetics, University of Nottingham, Nottingham, UK

⁴  University of Edinburgh, WTCCB, Edinburgh, UK

⁵  Cardiff School of Biosciences, Cardiff University, Cardiff, UK

⁶  Department of Biochemistry, University of Oxford, Oxford, UK

author email corresponding author email

Epigenetics & Chromatin 2009, 2:18doi:10.1186/1756-8935-2-18

Published:	2 December 2009

Abstract

Background

In Saccharomyces cerevisiae genes that are located close to a telomere can become transcriptionally repressed by an epigenetic process known as telomere position effect. There is large variation in the level of the telomere position effect among telomeres, with many native ends exhibiting little repression.

Results

Chromatin analysis, using microccocal nuclease and indirect end labelling, reveals distinct patterns for ends with different silencing states. Differences were observed in the promoter accessibility of a subtelomeric reporter gene and a characteristic array of phased nucleosomes was observed on the centromere proximal side of core X at a repressive end. The silent information regulator proteins 2 - 4, the yKu heterodimer and the subtelomeric core X element are all required for the maintenance of the chromatin structure of repressive ends. However, gene deletions of particular histone modification proteins can eliminate the silencing without the disruption of this chromatin structure.

Conclusion

Our data identifies chromatin features that correlate with the silencing state and indicate that an array of phased nucleosomes is not sufficient for full repression.