RNA helicase DHX15 exemplifies a unique dependency in acute leukemia.

RNA-binding proteins (RBP) have emerged as essential regulators that control gene expression and modulate multiple cancer traits. T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy derived from transformation of T-cell progenitors that normally undergo discrete steps of differentiation in the thymus. The implications of essential RBP during T-cell neoplastic transformation remain largely unclear. Systematic evaluation of RBP identifies RNA helicase DHX15, which facilitates the disassembly of the spliceosome and release of lariat introns, as a T-ALL dependency factor. Functional analysis using multiple murine T-ALL models demonstrates the essential importance of DHX15 in tumor cell survival and leukemogenesis. Moreover, single-cell transcriptomics reveals that DHX15 depletion in T-cell progenitors hinders burst proliferation during the transition from doublenegative to double-positive cells (CD4-CD8- to CD4+CD8+). Mechanistically, abrogation of DHX15 perturbs RNA splicing and leads to diminished levels of SLC7A6 and SLC38A5 transcripts due to intron retention, thereby suppressing glutamine import and mTORC1 activity. We further propose a DHX15 signature modulator drug ciclopirox and demonstrate that it has prominent anti-T-ALL efficacy. Collectively, our data highlight the functional contribution of DHX15 to leukemogenesis through regulation of established oncogenic pathways. These findings also suggest a promising therapeutic approach, i.e., splicing perturbation by targeting spliceosome disassembly, may achieve considerable anti-tumor efficacy.

ASCancer Atlas: a comprehensive knowledgebase of alternative splicing in human cancers.

Alternative splicing (AS) is a fundamental process that governs almost all aspects of cellular functions, and dysregulation in this process has been implicated in tumor initiation, progression and treatment resistance. With accumulating studies of carcinogenic mis-splicing in cancers, there is an urgent demand to integrate cancer-associated splicing changes to better understand their internal cross-talks and functional consequences from a global view. However, a resource of key functional AS events in human cancers is still lacking. To fill the gap, we developed ASCancer Atlas (https://ngdc.cncb.ac.cn/ascancer), a comprehensive knowledgebase of aberrant splicing in human cancers. Compared to extant databases, ASCancer Atlas features a high-confidence collection of 2006 cancer-associated splicing events experimentally proved to promote tumorigenesis, a systematic splicing regulatory network, and a suit of multi-scale online analysis tools. For each event, we manually curated the functional axis including upstream splicing regulators, splicing event annotations, downstream oncogenic effects, and possible therapeutic strategies. ASCancer Atlas also houses about 2 million computationally putative splicing events. Additionally, a user-friendly web interface was built to enable users to easily browse, search, visualize, analyze, and download all splicing events. Overall, ASCancer Atlas provides a unique resource to study the functional roles of splicing dysregulation in human cancers.

DHX15 is involved in SUGP1-mediated RNA missplicing by mutant SF3B1 in cancer.

SF3B1 is the most frequently mutated spliceosomal gene in cancer. Several hotspot mutations are known to disrupt the interaction of SF3B1 with another splicing factor, SUGP1, resulting in the RNA missplicing that characterizes mutant SF3B1 cancers. Properties of SUGP1, especially the presence of a G-patch motif, a structure known to function by activating DEAH-box RNA helicases, suggest the requirement of such an enzyme in SUGP1 function in splicing. However, the identity of this putative helicase has remained an important unanswered question. Here, using a variety of protein-protein interaction assays, we identify DHX15 as the critical helicase. We further show that depletion of DHX15 or expression of any of several DHX15 mutants, including one implicated in acute myeloid leukemia, partially recapitulates the splicing defects of mutant SF3B1. Moreover, a DHX15-SUGP1 G-patch fusion protein is able to incorporate into the spliceosome to rescue the splicing defects of mutant SF3B1. We also present the crystal structure of the human DHX15-SUGP1 G-patch complex, which reveals the molecular basis of their direct interaction. Our data thus demonstrate that DHX15 is the RNA helicase that functions with SUGP1 and additionally provide important insight into how mutant SF3B1 disrupts splicing in cancer.

Molecular evolutionary and structural analysis of human UCHL1 gene demonstrates the relevant role of intragenic epistasis in Parkinson's disease and other neurological disorders.

BACKGROUND: Parkinson's disease (PD) is the second most common neurodegenerative disorder. PD associated human UCHL1 (Ubiquitin C-terminal hydrolase L1) gene belongs to the family of deubiquitinases and is known to be highly expressed in neurons (1-2% in soluble form). Several functions of UCHL1 have been proposed including ubiquitin hydrolyze activity, ubiquitin ligase activity and stabilization of the mono-ubiquitin. Mutations in human UCHL1 gene have been associated with PD and other neurodegenerative disorders. The present study aims to decipher the sequence evolutionary pattern and structural dynamics of UCHL1. Furthermore, structural and interactional analysis of UCHL1 was performed to help elucidate the pathogenesis of PD. RESULTS: The phylogenetic tree topology suggests that the UCHL1 gene had originated in early gnathostome evolutionary history. Evolutionary rate analysis of orthologous sequences reveals strong purifying selection on UCHL1. Comparative structural analysis of UCHL1 pinpoints an important protein segment spanning amino acid residues 32 to 39 within secretion site with crucial implications in evolution and PD pathogenesis through a well known phenomenon called intragenic epistasis. Identified critical protein segment appears to play an indispensable role in protein stability, proper protein conformation as well as harboring critical interaction sites. CONCLUSIONS: Conclusively, the critical protein segment of UCHL1 identified in the present study not only demonstrates the relevant role of intraprotein conformational epistasis in the pathophysiology of PD but also offers a novel therapeutic target for the disease.

Gene dysregulation in peripheral blood of moyamoya disease and comparison with other vascular disorders.

OBJECTIVE: Moyamoya disease (MMD) is a chronic occlusive cerebrovascular disease with unknown etiology, sharing many similar clinical symptoms with other vascular disorders. This study aimed to investigate gene dysregulation in peripheral blood of MMD and compare it with other vascular disorders. METHODS: Transcriptomic profiles of 12 MMD patients and 8 healthy controls were obtained using RNA sequencing. Differentially expressed genes (DEGs) were identified and several were validated by quantitative real-time PCR in independent samples. Biological pathway enrichment analysis of DEGs and deconvolution of leukocyte subsets in peripheral blood were performed. Expression profiles for other vascular diseases were downloaded from public database and consistent DEGs were calculated. Gene set enrichment analysis (GSEA) was conducted to compare gene dysregulation pattern between MMD and other vascular diseases. RESULTS: A total of 533 DEGs were identified for MMD. Up-regulated genes were mainly involved in extracellular matrix (ECM) organization, whereas down-regulated genes were primarily associated with inflammatory and immune responses. As for cell populations, significantly increased naïve B cells and naïve CD4 cells as well as obviously decreased resting natural killer cells were observed in peripheral blood of MMD patients. GSEA analysis indicated that only up-regulated genes of ischemic stroke and down-regulated genes of coronary artery disease and myocardial infarction were enriched in up-regulated and down-regulated genes of MMD, respectively. CONCLUSION: Dysregulated genes in peripheral blood of MMD mainly played key roles in ECM organization, inflammatory and immune responses. This gene dysregulation pattern was specific compared with other vascular diseases. Besides, naïve B cells, naïve CD4 cells and resting natural killer cells were aberrantly disrupted in peripheral blood of MMD patients. These results will help elucidate the complicated pathogenic mechanism of MMD.

The frontline of immune response in peripheral blood.

Peripheral blood is an attractive source for the discovery of disease biomarkers. Gene expression profiling of whole blood or its components has been widely conducted for various diseases. However, due to population heterogeneity and the dynamic nature of gene expression, certain biomarkers discovered from blood transcriptome studies could not be replicated in independent studies. In the meantime, it's also important to know whether a reliable biomarker is shared by several diseases or specific to certain health conditions. We hypothesized that common mechanism of immune response in blood may be shared by different diseases. Under this hypothesis, we surveyed publicly available transcriptome data on infectious and autoimmune diseases derived from peripheral blood. We examined to which extent common gene dys-regulation existed in different diseases. We also investigated whether the commonly dys-regulated genes could serve as reliable biomarkers. First, we found that a limited number of genes are frequently dys-regulated in infectious and autoimmune diseases, from which we selected 10 genes co-dysregulated in viral infections and another set of 10 genes co-dysregulated in bacterial infections. In addition to its ability to distinguish viral infections from bacterial infections, these 20 genes could assist in disease classification and monitoring of treatment effect for several infectious and autoimmune diseases. In some cases, a single gene is sufficient to serve this purpose. It was interesting that dys-regulation of these 20 genes were also observed in other types of diseases including cancer and stroke where certain genes could also serve as biomarkers for diagnosis or prognosis. Furthermore, we demonstrated that this set of 20 genes could also be used in continuous monitoring of personal health. The rich information from these commonly dys-regulated genes may find its wide application in clinical practice and personal healthcare. More validation studies and in-depth investigations are warranted in the future.

Towards Personalized Intervention for Alzheimer's Disease.

Alzheimer's disease (AD) remains to be a grand challenge for the international community despite over a century of exploration. A key factor likely accounting for such a situation is the vast heterogeneity in the disease etiology, which involves very complex and divergent pathways. Therefore, intervention strategies shall be tailored for subgroups of AD patients. Both demographic and in-depth information is needed for patient stratification. The demographic information includes primarily APOE genotype, age, gender, education, environmental exposure, life style, and medical history, whereas in-depth information stems from genome sequencing, brain imaging, peripheral biomarkers, and even functional assays on neurons derived from patient-specific induced pluripotent cells (iPSCs). Comprehensive information collection, better understanding of the disease mechanisms, and diversified strategies of drug development would help with more effective intervention in the foreseeable future.