CTCF driven TERRA transcription facilitates completion of telomere DNA replication

Abstract

Telomere repeat DNA forms a nucleo-protein structure that can obstruct chromosomal DNA replication, especially under conditions of replication stress. Transcription of telomere repeats can initiate at subtelomeric CTCF-binding sites to generate telomere repeat-encoding RNA (TERRA), but the role of transcription, CTCF, and TERRA in telomere replication is not known. Here, we have used CRISPR/Cas9 gene editing to mutate CTCF-binding sites at the putative start site of TERRA transcripts for a class of subtelomeres. Under replication stress, telomeres lacking CTCF-driven TERRA exhibit sister-telomere loss and upon entry into mitosis, exhibit the formation of ultra-fine anaphase bridges and micronuclei. Importantly, these phenotypes could be rescued by the forced transcription of TERRA independent of CTCF binding. Our findings indicate that subtelomeric CTCF facilitates telomeric DNA replication by promoting TERRA transcription. Our findings also demonstrate that CTCF-driven TERRA transcription acts in cis to facilitate telomere repeat replication and chromosome stability.

CTCF‐induced upregulation of HOXA11‐AS facilitates cell proliferation and migration by targeting miR‐518b/ACTN4 axis in prostate cancer

“…30 Besides, CTCF has been reported to serve as a transcription activator of genes. 31,32 In this study, CTCF was confirmed to bind with the HOXA11-AS promoter in PCa.…”

Live-cell imaging reveals the dynamics and function of single-telomere TERRA molecules in cancer cells

“…In future experiments, it will be important to investigate whether depletion of TERRA-MS2 transcripts results in DNA damage at the MS2-tagged telomere. Indeed, recent evidence indicates that TERRA expression facilitates replication in cis of the TERRA transcribing telomere [20], thus single-telomere TERRA downregulation may perturb DNA replication at the TERRA-depleted telomere, resulting in DNA damage.…”

“…RNA fluorescence in-situ hybridization (FISH) and live-cell imaging analyses have shown that a subset of TERRA transcripts localizes with human telomeres [5,6,17]. At telomeres, TERRA molecules have been proposed to mediate several important functions, including regulation of heterochromatin formation [16], recruitment of chromosome end-processing and chromatin remodelling factors to dysfunctional telomeres [18,19], sustaining telomeric DNA replication [20], participating in telomere length homeostasis by regulating telomerase activity [13,14] or promoting homologous recombination among telomeres through formation of RNA-DNA heteroduplex (R-loops) at chromosome ends [21-24]. In addition to their preferential association with telomeres, recent evidence indicates that TERRA transcripts interact with numerous internal chromosomal regions to regulate widespread gene expression [25].…”

DNA:RNA hybrids at telomeres – when it is better to be out of the (R) loop

“…The binding of TERRA to telomeres in cis is supported by several lines of evidence in yeast as well as in human cells . Therefore, identifying the telomeres that transcribe TERRA should inform us which telomeres are potentially capable of generating TRLs.…”