Non-coding telomeric and subtelomeric transcripts are differentially regulated by telomeric and heterochromatin assembly factors in fission yeast

Abstract

While telomere repeat-containing non-coding RNA has been identified in a variety of eukaryotes, its biological role is not yet clear. We have identified telomeric transcripts in fission yeast, a model system that combines precise genetic manipulability with telomeres remarkably similar to those of human. Like human and budding yeast, fission yeast harbours a population of telomeric RNA molecules containing G-rich telomeric repeats transcribed from the subtelomere to the telomere. In addition, we detect substantial levels of C-rich telomeric RNA whose appearance is independent of the RNA-dependent RNA polymerase, suggesting that the telomere repeats themselves serve as promoter sites; multiple distinct subtelomeric RNAs are also present. The regulation of these transcripts depends on the telomere-associated proteins Taz1 and Rap1, as deletion of taz1+ or rap1+ leads to increased levels of both telomere repeat-containing and subtelomeric transcripts. In contrast, loss of the heterochromatin proteins Swi6 or Clr4 or the telomerase regulator Rif1 results in elevated subtelomeric RNA levels while telomere-repeat containing transcript levels remain repressed. Coupled with the large body of knowledge surrounding the functions of telomeric and heterochromatin factors in fission yeast, these in vivo analyses suggest testable models for the roles of TERRA in telomere function.

Translin and Trax differentially regulate telomere-associated transcript homeostasis

“…Other sub-telomeric transcripts, termed ARRETs have also been detected in S. pombe for the sub-telomeric regions on chromosomes 1, 2 and occasionally 3 [41, 42]. ARRET and TERRA sequences are not covered on the tiling arrays used in this study.…”

“…To further confirm the regulation of sub-telomeric transcripts by Tfx1, we examined ARRET (immediately sub-telomeric regions) levels in tfx1 Δ and tsn1 Δ strains using RT-PCR/RT-qPCR [43]. Loss of Taz1 gives elevated ARRET levels, consistent with activation of tlh genes in the absence of Taz1 [39, 42]. Loss of Tfx1 resulted in an approximately two-fold elevation in ARRETs, again, consistent with the tlh transcripts (Figure 4).…”

“…A schematic of an S. pombe telomere showing the telomere (purple) and the sub-telomeric region (light blue; previously referred to as STE) [42]. The ARRET and TERRA transcripts are aligned to their approximate template location.…”

Replication of Telomeres and the Regulation of Telomerase

“…They protect from rapid loss of telomeric DNA. TERRA and other telomeric transcripts have been recently characterized in fission yeast (Bah et al 2012;Greenwood and Cooper 2012). Their expression is negatively regulated by Taz1 and Rap1.…”

Formation of telomeric repeat-containing RNA (TERRA) foci in highly proliferating mouse cerebellar neuronal progenitors and medulloblastoma

“…In fission yeast, transcripts can be detected for both sense and antisense strands of the telomere repeat tract and adjacent telomere sequence (Bah et al, 2012;Greenwood and Cooper, 2012). TERRA RNA can interact with shelterin proteins to regulate telomere heterochromatin formation (Deng et al, 2009) and capping by the telomere single strand DNA binding protein Pot 1 (Flynn et al, 2011;López de Silanes et al, 2010).…”