Telomeric position effect--a third silencing mechanism in eukaryotes.

Eukaryotic chromosomes terminate in telomeres, complex nucleoprotein structures that are required for chromosome integrity that are implicated in cellular senescence and cancer. The chromatin at the telomere is unique with characteristics of both heterochromatin and euchromatin. The end of the chrom...

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Autores principales:	J Greg Doheny, Randy Mottus, Thomas A Grigliatti
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2008
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/1eaa39f529ca494baf0b6c382c1fe954
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spelling	oai:doaj.org-article:1eaa39f529ca494baf0b6c382c1fe9542021-11-25T06:18:18ZTelomeric position effect--a third silencing mechanism in eukaryotes.1932-620310.1371/journal.pone.0003864https://doaj.org/article/1eaa39f529ca494baf0b6c382c1fe9542008-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/19057646/?tool=EBIhttps://doaj.org/toc/1932-6203Eukaryotic chromosomes terminate in telomeres, complex nucleoprotein structures that are required for chromosome integrity that are implicated in cellular senescence and cancer. The chromatin at the telomere is unique with characteristics of both heterochromatin and euchromatin. The end of the chromosome is capped by a structure that protects the end and is required for maintaining proper chromosome length. Immediately proximal to the cap are the telomere associated satellite-like (TAS) sequences. Genes inserted into the TAS sequences are silenced indicating the chromatin environment is incompatible with transcription. This silencing phenomenon is called telomeric position effect (TPE). Two other silencing mechanisms have been identified in eukaryotes, suppressors position effect variegation [Su(var)s, greater than 30 members] and Polycomb group proteins (PcG, approximately 15 members). We tested a large number of each group for their ability to suppress TPE [Su(TPE)]. Our results showed that only three Su(var)s and only one PcG member are involved in TPE, suggesting silencing in the TAS sequences occurs via a novel silencing mechanism. Since, prior to this study, only five genes have been identified that are Su(TPE)s, we conducted a candidate screen for Su(TPE) in Drosophila by testing point mutations in, and deficiencies for, proteins involved in chromatin metabolism. Screening with point mutations identified seven new Su(TPE)s and the deficiencies identified 19 regions of the Drosophila genome that harbor suppressor mutations. Chromatin immunoprecipitation experiments on a subset of the new Su(TPE)s confirm they act directly on the gene inserted into the telomere. Since the Su(TPE)s do not overlap significantly with either PcGs or Su(var)s, and the candidates were selected because they are involved generally in chromatin metabolism and act at a wide variety of sites within the genome, we propose that the Su(TPE) represent a third, widely used, silencing mechanism in the eukaryotic genome.J Greg DohenyRandy MottusThomas A GrigliattiPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 3, Iss 12, p e3864 (2008)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q J Greg Doheny Randy Mottus Thomas A Grigliatti Telomeric position effect--a third silencing mechanism in eukaryotes.
description	Eukaryotic chromosomes terminate in telomeres, complex nucleoprotein structures that are required for chromosome integrity that are implicated in cellular senescence and cancer. The chromatin at the telomere is unique with characteristics of both heterochromatin and euchromatin. The end of the chromosome is capped by a structure that protects the end and is required for maintaining proper chromosome length. Immediately proximal to the cap are the telomere associated satellite-like (TAS) sequences. Genes inserted into the TAS sequences are silenced indicating the chromatin environment is incompatible with transcription. This silencing phenomenon is called telomeric position effect (TPE). Two other silencing mechanisms have been identified in eukaryotes, suppressors position effect variegation [Su(var)s, greater than 30 members] and Polycomb group proteins (PcG, approximately 15 members). We tested a large number of each group for their ability to suppress TPE [Su(TPE)]. Our results showed that only three Su(var)s and only one PcG member are involved in TPE, suggesting silencing in the TAS sequences occurs via a novel silencing mechanism. Since, prior to this study, only five genes have been identified that are Su(TPE)s, we conducted a candidate screen for Su(TPE) in Drosophila by testing point mutations in, and deficiencies for, proteins involved in chromatin metabolism. Screening with point mutations identified seven new Su(TPE)s and the deficiencies identified 19 regions of the Drosophila genome that harbor suppressor mutations. Chromatin immunoprecipitation experiments on a subset of the new Su(TPE)s confirm they act directly on the gene inserted into the telomere. Since the Su(TPE)s do not overlap significantly with either PcGs or Su(var)s, and the candidates were selected because they are involved generally in chromatin metabolism and act at a wide variety of sites within the genome, we propose that the Su(TPE) represent a third, widely used, silencing mechanism in the eukaryotic genome.
format	article
author	J Greg Doheny Randy Mottus Thomas A Grigliatti
author_facet	J Greg Doheny Randy Mottus Thomas A Grigliatti
author_sort	J Greg Doheny
title	Telomeric position effect--a third silencing mechanism in eukaryotes.
title_short	Telomeric position effect--a third silencing mechanism in eukaryotes.
title_full	Telomeric position effect--a third silencing mechanism in eukaryotes.
title_fullStr	Telomeric position effect--a third silencing mechanism in eukaryotes.
title_full_unstemmed	Telomeric position effect--a third silencing mechanism in eukaryotes.
title_sort	telomeric position effect--a third silencing mechanism in eukaryotes.
publisher	Public Library of Science (PLoS)
publishDate	2008
url	https://doaj.org/article/1eaa39f529ca494baf0b6c382c1fe954
work_keys_str_mv	AT jgregdoheny telomericpositioneffectathirdsilencingmechanismineukaryotes AT randymottus telomericpositioneffectathirdsilencingmechanismineukaryotes AT thomasagrigliatti telomericpositioneffectathirdsilencingmechanismineukaryotes
_version_	1718413910656155648

Telomeric position effect--a third silencing mechanism in eukaryotes.

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