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Hotspot mutations in the promoter region of the Telomerase Reverse Transcriptase (TERT) gene are the third most common recurrent mutation in cancer and occur in over 80% of IDH-wild type glioblastomas (GBMs). These single point mutations reactivate the telomerase complex, enabling cellular immortalization through the indefinite maintenance of telomere length. The transcription factor-binding site created by these point mutations specifically recruits the multimeric transcription factor GABP to the mutant TERT promoter. GABP is composed of the DNA-binding GABPα subunit and the trans-activating GABPβ subunit. GABP can form two transcription factor species – a dimer or a tetramer – depending on which of the structurally distinct GABPβ isoforms is incorporated into the complex. In this study, we show that depletion of the GABP tetramer-forming isoform GABPβ1L silences mutant TERT promoter in GBM cells. TERT promoter mutant cells lacking GABPβ1L fail to express TERT at levels sufficient for immortalization, thus leading to telomere shortening, DNA damage accumulation, and cell death in vitro. Additionally, mice bearing orthotopically xenografted TERT promoter mutant tumors lacking GABPβ1L had reduced tumor burden and prolonged survival in comparison to mice bearing GABPβ1L wild-type tumors. Importantly, loss of GABPβ1L has minimal phenotypic effects in a panel of TERT promoter wild-type cell lines, including a transformed human astrocyte line expressing TERT from its endogenous promoter. Exogenous expression of GABPB1L or TERT is sufficient to halt telomere degradation and loss of cell viability in GABPβ1L-deficient lines bearing the mutant TERT promoter. We have now begun to investigate upstream pathways that regulate GABP tetramer formation as well as co-factors required for GABP-mediated regulation of TERT as targets to reverse immortality in TERT promoter mutant GBM. Together, these results highlight the potentially widespread role of the GABP tetramer in enabling replicative immortality of TERT promoter mutant GBM.

Thousands of long noncoding RNAs (lncRNAs) have been discovered, yet the function of the vast majority remains unclear. Here, we show that a p53-regulated lncRNA which we named PINCR (p53-induced noncoding RNA), is induced ~100-fold after DNA damage and exerts a prosurvival function in human colorectal cancer cells (CRC) in vitro and tumor growth in vivo. Targeted deletion of PINCR in CRC cells significantly impaired G1 arrest and induced hypersensitivity to chemotherapeutic drugs. PINCR regulates the induction of a subset of p53 targets involved in G1 arrest and apoptosis, including BTG2, RRM2B and GPX1. Using a novel RNA pulldown approach that utilized endogenous S1-tagged PINCR, we show that PINCR associates with the enhancer region of these genes by binding to RNA-binding protein Matrin 3 that, in turn, associates with p53. Our findings uncover a critical prosurvival function of a p53/PINCR/Matrin 3 axis in response to DNA damage in CRC cells. DOI: http://dx.doi.org/10.7554/eLife.23244.001, eLife digest Though DNA contains the information needed to build the proteins that keep cells alive, only 2% of the DNA in a human cell codes for proteins. The remaining 98% is referred to as non-coding DNA. The information in some of these non-coding regions can still be copied into molecules of RNA, including long molecules called lncRNAs. Little is known about what lncRNAs actually do, but growing evidence suggests that these molecules are important for a number of vital processes including cell growth and survival. When the DNA in an animal cell gets damaged, the cell needs to decide whether to pause growth and repair the damage, or to kill itself if the harm is too great. One of the best-studied proteins guiding this decision is the p53 protein, which increases the number of protein-coding genes needed to carry out either option in this decision. That is to say that, p53 regulates the genes needed to kill the cell and the genes needed to temporarily pause its growth and repair the damage, which instead keeps the cell alive. So, how does the p53 protein guide the decision, and are lncRNA molecules involved? Using human colon cancer cells, Chaudhary et al. now report that when DNA is damaged, the levels of a specific lncRNA increase 100-fold. Further experiments showed that this lncRNA – named PINCR, which refers to p53-induced noncoding RNA – promotes the survival of cells. Chaudhary et al. showed that PINCR molecules do this by recruiting a protein called Matrin 3 to a certain region in the DNA called an enhancer and then links it to promoter region in the DNA of specific genes that temporarily pause cell growth but keep the cell alive. This in turn activates these ‘pro-survival genes’. In further experiments, when the PINCR molecules were essentially deleted, p53 was not able to fully activate these genes and as a result more of the cells died. Together these findings increase our knowledge of how lncRNAs can work, especially in the context of DNA damage in cancer cells. A next important step will be to uncover other roles for the PINCR molecule in both cancer and healthy cells. DOI: http://dx.doi.org/10.7554/eLife.23244.002

The ability to selectively regulate expression of any target gene within a genome provides a means to address a variety of diseases and disorders. While artificial transcription factors are emerging as powerful tools for gene activation within a natural chromosomal context, current generations often exhibit relatively weak, variable, or unpredictable activity across targets. To address these limitations, we developed a novel system for gene activation, which bypasses native promoters to achieve unprecedented levels of transcriptional upregulation by integrating synthetic promoters at target sites. This gene activation system is multiplexable and easily tuned for precise control of expression levels. Importantly, since promoter vector integration requires just one variable sgRNA to target each gene of interest, this procedure can be implemented with minimal cloning. Collectively, these results demonstrate a novel system for gene activation with wide adaptability for studies of transcriptional regulation and cell line engineering.

A male zebra finch learns a song by listening to a tutor, but song learning is normally restricted to a critical period in juvenile development. Here we identify an RNA whose expression in the song control circuit is altered during this critical period. The RNA encodes a soluble presynaptic protein that forms a predicted amphipathic a helix typical of the lipid-binding domain in apolipoproteins. We show this protein, which we call synelfin, to be the homolog of the human non-Aβ component (and its precursor) recently purified from Alzheimer's disease amyloid. We suggest this highly conserved protein may serve a novel function critical to the regulation of vertebrate neural plasticity.