剪切因子调控转录后可变剪切过程，其表达量异常与肿瘤进展密切相关。本研究前期利用CRISPR/Cas9文库技术筛选发现剪切因子SNRPB2在乳腺肿瘤进展中不可或缺。有关SNRPB2在肿瘤研究中报道甚少，相关分子机理有待研究。预实验发现：高表达SNRPB2的乳腺癌预后更差；敲除SNRPB2基因显著抑制乳腺癌细胞生长与迁移；SNRPB2基因缺失会改变靶基因Bcl-X的剪切模式而引起显著凋亡效应。我们假设SNRPB2通过调控Bcl-X剪切并拮抗RBM4对Bcl-X的剪切效应，促进乳腺肿瘤进展。本项目计划运用细胞和分子生物学实验、转录组测序技术、动物实验和临床样本分析，研究SNRPB2对靶基因Bcl-X可变剪切的直接与间接调控机制，鉴定介导SNRPB2促癌效应的关键靶基因，阐明SNRPB2直接调节的细胞信号分子通路。本研究将揭示SNRPB2与乳腺肿瘤进展的内在联系，为乳腺肿瘤治疗提供潜在新靶点。

As one of the most prevalent mechanisms of gene regulation, alternative splicing (AS) plays a vital role in the intricate regulation of protein function, and splicing dysregulation is closely associated with human cancer. This RNA processing event is mediated by a complex interplay of splicing factors (SFs) and defined RNA sequences (splice sites) within pre-mRNA transcripts. These SFs and other RNA-binding proteins are tightly regulated and embedded in signaling pathways in the cancer cell, making AS a major modulator of cancer cell properties and functions. Using an in vivo CRISPR screen targeting RNA-binding proteins, we have previously identified Small Nuclear Ribonucleoprotein Polypeptide B2 (SNRPB2) as a SF involved in breast tumor progression. To date, there is almost no lecture to uncover the role of SNRPB2 in tumor and the underlying molecular mechanisms remain poorly defined. In this study, SNRPB2 was frequently up-regulated in breast cancer and was associated with poor clinical outcome in patients. Knockout of SNRPB2 gene by CRISPR/Cas9 significantly inhibited breast cancer cell growth and migration and caused apoptosis. RNA-seq analysis revealed that SNRPB2 ablation altered the splicing patterns of cancer-related genes in transcriptome-scale, including downstream target gene Bcl-X. Additionally, SNRPB2 was found to bind to SF RBM4. We therefore hypothesize that SNRPB2 promotes breast tumor progression by regulating Bcl-X AS and antagonizing the AS effect of RBM4 on Bcl-X. We plan to perform relevant cell and molecular biology experiments, transcriptome sequencing, animal experiments and clinical sample analysis to investigate the biological role of SNRPB2 on breast tumor progression as well as the mechanism of SNRPB2 regulating the AS of Bcl-X. Further, we are going to identify the key downstream molecules that mediate the effect of SNRPB2 on breast tumor progression and to elucidate the primary signaling pathway that is directly regulated by SNRPB2. In summary, these proposed experiments in the project are to lay a solid foundation for identifying a prognostic marker and a translatable therapeutic target for breast tumor.