TERRA and the histone methyltransferase Dot1 cooperate to regulate senescence in budding yeast.

Jennifer J Wanat,Zhong Deng,Paul M Lieberman,F Brad Johnson,Jordan H Driskill,Glennis A Logsdon,Shawn Ahmed

doi:10.1371/journal.pone.0195698

Abstract

The events underlying senescence induced by critical telomere shortening are not fully understood. Here we provide evidence that TERRA, a non-coding RNA transcribed from subtelomeres, contributes to senescence in yeast lacking telomerase (tlc1Δ). Levels of TERRA expressed from multiple telomere ends appear elevated at senescence, and expression of an artificial RNA complementary to TERRA (anti-TERRA) binds TERRA in vivo and delays senescence. Anti-TERRA acts independently from several other mechanisms known to delay senescence, including those elicited by deletions of EXO1, TEL1, SAS2, and genes encoding RNase H enzymes. Further, it acts independently of the senescence delay provided by RAD52-dependent recombination. However, anti-TERRA delays senescence in a fashion epistatic to inactivation of the conserved histone methyltransferase Dot1. Dot1 associates with TERRA, and anti-TERRA disrupts this interaction in vitro and in vivo. Surprisingly, the anti-TERRA delay is independent of the C-terminal methyltransferase domain of Dot1 and instead requires only its N-terminus, which was previously found to facilitate release of telomeres from the nuclear periphery. Together, these data suggest that TERRA and Dot1 cooperate to drive senescence.

Highlights

Telomeres shorten with DNA replication because of the end replication problem and other factors such as oxidative damage, exonucleolytic processing, and aberrant replication and recombination events [1]
Because of the aforementioned chromatin changes, and since Telomere Repeat-Containing RNA (TERRA) is a set of non-coding RNA molecules transcribed from subtelomeric promoters and extending into the telomere repeats at chromosome ends [17,18,19], we hypothesized that TERRA levels might change and possibly play a functional role in triggering cellular senescence in yeast. qRT-PCR analyses of RNA from non-senescent tlc1Δ versus senescent tlc1Δ cells showed that levels of transcripts from multiple subtelomeres are significantly increased at senescence (Fig 1A)
We demonstrate that TERRA associates physically with Dot1 in vivo and in vitro, and that this interaction is inhibited by anti-TERRA expression

Summary

Introduction

Telomeres shorten with DNA replication because of the end replication problem and other factors such as oxidative damage, exonucleolytic processing, and aberrant replication and recombination events [1]. Telomerase can counter this shortening but its level in most human tissues is not sufficient to compensate for the loss of length with age. Telomeres shorten to critical lengths that can lead to apoptosis or permanent cell cycle arrest (senescence), depending on cell context [2]. TERRA and Dot cooperate to regulate senescence.

Methods

Results

Conclusion