PROJECT SUMMARY/ABSTRACT Glioblastoma (GBM), a high-grade glioma (grade IV), is the most prevalent and malignant primary brain tumor in adults. There is no effective treatment of GBM. After standard treatment, the median survival of GBM patients is around 15 months. GBM is featured by enhanced cell proliferation, high propensity of invasion/diffuse infiltration throughout the brain, and resistance to chemo-/radiation therapy. Emerging evidence supports that long non-coding RNAs (lncRNAs, ~18,000 human lncRNA genes) can mediate tumor- promoting/suppressing effects and serve as independent diagnostic/prognostic biomarkers. Our previous integrative genomic study revealed that many lncRNAs show dysregulated expression, are associated with clinical prognosis, or harbor frequent somatic copy number alterations in GBM, suggesting an important role of lncRNAs in GBM pathogenesis. However, the function and mechanism of most lncRNAs in GBM are unknown. To fill this gap, our long-term goal is to leverage systematic multi-omic approaches to characterize the function and mechanism of lncRNAs in GBM, and to help develop new therapeutic strategies based on novel insight into lncRNA regulation in GBM. Our large-scale loss-of-function screen using CRISPR interference (CRISPRi) identified an antisense lncRNA, lnc-YINC (YBX1-interacting lncRNA) that was critical for GBM cell growth and was significantly up-regulated in GBM compared with normal brain tissue and low-grade glioma (LGG). The higher expression of lnc-YINC was associated with shorter overall survival of GBM patients. Functionally, lnc- YINC acted in-trans and was a key regulator of cell cycle progression of GBM cells/glioma stem cells (GSCs) and self-renewal of GSCs. It also protected GBM cells/GSCs from DNA double-strand breaks (DSBs) caused by endogenous stress or exogenous ionizing radiation. Mechanistically, lnc-YINC interacted with YBX1, and post-transcriptionally regulated the expression of key regulators of cell cycle or DSB repair, at least partially by stabilizing their mRNAs. Based on these new findings, we hypothesize that lnc-YINC is a GBM-promoting lncRNA that promotes proliferation of and modulates radio-sensitivity of GBM cells/GSCs, by enhancing YBX1 binding to key regulators of cell cycle/DSB repair and co-regulating their expression at post-transcriptional level. The objectives of this proposal are (a) to determine the role of lnc-YINC in gliomagenesis, (b) to integrate enhanced CLIP-seq (eCLIP-seq), ribosome profiling, RNA-seq and quantitative mass spectrometry data, with functional assays to identify the downstream targets of lnc-YINC/YBX1 that are key to regulating cell cycle or DSB repair, (c) to dissect the molecular mechanisms whereby lnc-YINC/YBX1 axis post-transcriptionally regulates the expression of key regulators of cell cycle or DSB repair, (d) to determine the role of lnc-YINC in modulating radio-sensitivity of GBM cells/GSCs and to investigate the therapeutic impact of com...