Sun Shenyu, Paniagua Karla, Ding Ling, Wang Xian, Huang Yufei, Flores Mario A, Gao Shou-Jiang
Cancer Virology Program, University of Pittsburgh Medical Center Hillman Cancer Center, Pittsburgh, Pennsylvania, USA.
Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
bioRxiv. 2025 Mar 17:2025.03.17.643747. doi: 10.1101/2025.03.17.643747.
RNA alternative splicing is a fundamental cellular process implicated in cancer development. Kaposi's sarcoma-associated herpesvirus (KSHV), the etiological agent of multiple human malignancies, including Kaposi's sarcoma (KS), remains a significant concern, particularly in AIDS patients. A CRISPR-Cas9 screening of matched primary rat mesenchymal stem cells (MM) and KSHV-transformed MM cells (KMM) identified key splicing factors involved in KSHV-induced cellular transformation. To elucidate the mechanisms by which KSHV-driven splicing reprogramming mediates cellular transformation, we performed transcriptomic sequencing, identifying 131 differential alternative splicing transcripts, with exon skipping as the predominant event. Notably, these transcripts were enriched in vascular permeability, multiple metabolic pathways and ERK1/2 signaling cascades, which play key roles in KSHV-induced oncogenesis. Further analyses of cells infected with KSHV mutants lacking latent genes including vFLIP, vCyclin and viral miRNAs, as well as cells overexpressing LANA, revealed their involvement in alternative splicing regulation. Among the identified splicing factors, FAM50A, a component of the spliceosome complex C, was found to be crucial for KSHV-mediated transformation. FAM50A knockout resulted in distinct splicing profiles in both MM and KMM cells, and significantly inhibited KSHV-driven proliferation, cellular transformation and tumorigenesis. Mechanistically, FAM50A knockout altered SHP2 splicing, promoting an isoform with enhanced enzymatic activity that led to reduced STAT3 Y705 phosphorylation in KMM cells. These findings reveal a novel paradigm in which KSHV hijacks host splicing machinery, specifically FAM50A-mediated SHP2 splicing, to sustain STAT3 activation and drive oncogenic transformation.
RNA可变剪接是一种与癌症发展相关的基本细胞过程。卡波西肉瘤相关疱疹病毒（KSHV）是包括卡波西肉瘤（KS）在内的多种人类恶性肿瘤的病原体，仍然是一个重大问题，尤其是在艾滋病患者中。对匹配的原代大鼠间充质干细胞（MM）和KSHV转化的MM细胞（KMM）进行的CRISPR-Cas9筛选确定了参与KSHV诱导细胞转化的关键剪接因子。为了阐明KSHV驱动的剪接重编程介导细胞转化的机制，我们进行了转录组测序，鉴定出131个差异可变剪接转录本，其中外显子跳跃是主要事件。值得注意的是，这些转录本在血管通透性、多种代谢途径和ERK1/2信号级联反应中富集，这些在KSHV诱导的肿瘤发生中起关键作用。对感染缺乏包括vFLIP、vCyclin和病毒miRNA等潜伏基因的KSHV突变体的细胞，以及过表达LANA的细胞进行的进一步分析，揭示了它们参与可变剪接调控。在鉴定出的剪接因子中，剪接体复合物C的一个组分FAM50A被发现对KSHV介导的转化至关重要。FAM50A基因敲除导致MM和KMM细胞中出现不同的剪接谱，并显著抑制KSHV驱动的增殖、细胞转化和肿瘤发生。从机制上讲，FAM50A基因敲除改变了SHP2的剪接，促进了一种具有增强酶活性的异构体，导致KMM细胞中STAT3 Y705磷酸化减少。这些发现揭示了一种新的模式，即KSHV劫持宿主剪接机制，特别是FAM50A介导的SHP2剪接，以维持STAT3激活并驱动致癌转化。
