A Tale of NEAT1 Tails

The eukaryotic genome is pervasively transcribed, and the vast majority of the RNA species are not generated from protein-coding genes, but rather from the so called "dark matter" of the genome. Emerging evidence indicates that such non-coding transcripts may participate in a broad spectrum of biological processes. A well-conserved and very abundant non-coding RNA is NEAT1, which is essential for the formation and structural integrity of membrane-less nuclear bodies known as paraspeckles (PS). Although cell-based studies identified NEAT1-PS as putative regulators of gene expression through retention of hyperdited mRNAs and/or transcription factors, it has been unclear under which specific physiological conditions PS are formed in vivo and whether they have any biological relevance. We have recently demonstrated that PS are assembled in skin epidermal cells in response to oncogenic stress and that Neat1 is required for tumor initiation and progression into aggressive and invasive lesions in a classical two-stage chemically-induced skin cancer model. We provided evidence that oncogenic-induction of PS is dependent on the stress modulator p53. NEAT1 is a bona fide target of p53 and activation of p53 by different stress stimuli, including DNA damaging agents, stimulates the formation of PS. NEAT1 targeting in established human cancer cell lines induced synthetic lethality when combined to genotoxic chemotherapeutics, including PARP inhibitors, and non-genotoxic activation of p53. Importantly, the effect was greater when we specifically silenced NEAT1_2, the long isoform of NEAT1 and structural component of PS, suggesting that PS modulation is a promising therapeutic avenue to enhance chemosensitivity. To identify novel modulators of the NEAT1 isoform switch, we isolated PS from cell nuclei and purified NEAT1 RNA Binding Proteins (RBPs). We identified factors involved in the 3' end processing of polyadenylated RNA as well as several components of the Integrator complex (INT). INT restrains NEAT1_2 production, and hence PS formation, by favoring the 3' end processing of the short polyadenylated form NEAT1_1. Stress-induced PS maintain their colocalization with INT, thus suggesting that Integrator remains trapped into PS upon stress. In agreement with these findings, PS assembly resulted in transcriptional read-through at known INT target genes, including histones. Finally, low INT levels predict poor outcome of patients exposed to chemotherapy, thus confirming that targeting the RNA 3' end processing of NEAT1 is an interesting therapeutic strategy to modulate chemosensitivity.

Jaar van publicatie:2020

Toegankelijkheid:Closed