miR-6893-3p is a bonafide negative regulator of splicing activator, RNPS1.

RNA-binding protein with serine-rich domain 1, RNPS1, is a global guardian of splicing fidelity and has implications in cervical cancer cell progression. We previously observed elevated RNPS1 expression in cervical cancer cells compared to normal cells. To understand the mechanisms that lead to the dysregulation of RNPS1 expression in cervical cancer cells, we focused on microRNAs. Using an in silico approach, we predicted potential miRNA candidates targeting RNPS1. Among the candidate miRNAs, we found miR-6893-3p as a potential regulator of RNPS1 expression. Interestingly, the expression of miR-6893-3p is downregulated in cervical cancer cells compared to normal cells and its level is negatively correlated with the expression of RNPS1. Further, qPCR, Western blot analysis, and luciferase reporter assay confirmed that miR-6893-3p negatively regulates RNPS1 in HeLa cells. In this regard, overexpression of miR-6893-3p suppresses the endogenous mRNA and protein levels of RNPS1 in HeLa cells. Further investigation revealed that miR-6893-3p mediated regulation of RNPS1 is dependent on the binding of miR-6893-3p to a microRNA response element in the 3'UTR of RNPS1 mRNA. Furthermore, mechanistic analysis showed that targeted negative regulation of RNPS1 by miR-6893-3p occurs via enhanced mRNA degradation. Collectively, our findings establish miR-6893-3p as an important player in the post-transcriptional regulation of RNPS1 in HeLa cells. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03761-2.

Functional role of SAP18 protein: From transcriptional repression to splicing regulation.

Sin3 associated protein 18 (SAP18) is an evolutionary conserved protein, originally discovered in a complex with the transcriptional regulatory protein, Sin3. Subsequent investigations revealed SAP18 as an integral splicing component of the exon junction complex (EJC)-associated apoptosis-and splicing-associated protein (ASAP)/PNN-RNPS1-SAP18 (PSAP) complex. In association with Sin3, SAP18 contributes toward transcriptional repression of genes implicated in embryonic development, stress response, human immunodeficiency virus type 1 replication, and tumorigenesis. As a part of EJC, SAP18 mediates alternative splicing events and suppresses the cryptic splice sites present within flanking regions of exon-exon junctions. In this review, we provide a thorough discussion on SAP18, focussing on its conserved dual role in transcriptional regulation and messenger RNA splicing. Recent research on the involvement of SAP18 in the emergence of cancer and human disorders has also been highlighted. The potential of SAP18 as a therapeutic target is also discussed in these recent studies, particularly related to malignancies of the myeloid lineage.

Multifaceted roles of MAGOH Proteins.

MAGOH and MAGOHB are paralog proteins that can substitute each other in the exon junction complex (EJC). The EJC is formed of core components EIF4A3, RBM8A, and MAGOH/MAGOHB. As a part of the EJC, MAGOH proteins are required for mRNA splicing, export, translation and nonsense-mediated mRNA decay (NMD). MAGOH is also essential for embryonic development and normal cellular functioning. The haploinsufficiency of MAGOH results in disorders such as microcephaly and cancer. The present review discusses the discovery of MAGOH, its paralog MAGOHB, their roles in cellular function as part of the EJC, and other cellular roles that are not directly associated with mRNA processing. We also discuss how MAGOH haploinsufficiency in cancer cells can be exploited to develop a novel targeted cancer treatment.

RNPS1 functions as an oncogenic splicing factor in cervical cancer cells.

Numerous recent studies suggest that cancer-specific splicing alteration is a critical contributor to the pathogenesis of cancer. RNA-binding protein with serine-rich domain 1, RNPS1, is an essential regulator of the splicing process. However, the defined role of RNPS1 in tumorigenesis still remains elusive. We report here that the expression of RNPS1 is higher in cervical carcinoma samples from The Cancer Genome Atlas (TCGA-cervical squamous cell carcinoma and endocervical adenocarcinoma) compared to the normal tissues. Consistently, the expression of RNPS1 was high in cervical cancer cells compared to a normal cell line. This study shows for the first time that RNPS1 promotes cell proliferation and colony-forming ability of cervical cancer cells. Importantly, RNPS1 positively regulates migration-invasion of cervical cancer cells. Intriguingly, depletion of RNPS1 increases the chemosensitivity against the chemotherapeutic drug doxorubicin in cervical cancer cells. Further, we characterized the genome-wide isoform switching stimulated by RNPS1 in cervical cancer cell. Mechanistically, RNA-sequencing analysis showed that RNPS1 regulates the generation of tumor-associated isoforms of key genes, particularly Rac1b, RhoA, MDM4, and WDR1, through alternative splicing. RNPS1 regulates the splicing of Rac1 pre-mRNA via a specific alternative splicing switch and promotes the formation of its tumorigenic splice variant, Rac1b. While the transcriptional regulation of RhoA has been well studied, the role of alternative splicing in RhoA upregulation in cancer cells is largely unknown. Here, we have shown that the knockdown of RNPS1 in cervical cancer cells leads to the skipping of exons encoding the RAS domain of RhoA, consequently causing decreased expression of RhoA. Collectively, we conclude that the gain of RNPS1 expression may be associated with tumor progression in cervical carcinoma. RNPS1-mediated alternative splicing favors an active Rac1b/RhoA signaling axis that could contribute to cervical cancer cell invasion and metastasis. Thus, our work unveils a novel role of RNPS1 in the development of cervical cancer.