Molecular Cell

A Cancer-Specific Ubiquitin Ligase Drives mRNA Alternative Polyadenylation by Ubiquitinating the mRNA 3′ End Processing Complex

Alternative polyadenylation (APA) contributes to transcriptome complexity by generating mRNA isoforms with varying 3' UTR lengths. APA leading to 3' UTR shortening (3' US) is a common feature of most cancer cells; however, the molecular mechanisms are not understood. Here, we describe a widespread mechanism promoting 3' US in cancer through ubiquitination of the mRNA 3' end processing complex protein, PCF11, by the cancer-specific MAGE-A11-HUWE1 ubiquitin ligase. MAGE-A11 is normally expressed only in the male germline but is frequently re-activated in cancers. MAGE-A11 is necessary for cancer cell viability and is sufficient to drive tumorigenesis. Screening for targets of MAGE-A11 revealed that it ubiquitinates PCF11, resulting in loss of CFIm25 from the mRNA 3' end processing complex. This leads to APA of many transcripts affecting core oncogenic and tumor suppressors, including cyclin D2 and PTEN. These findings provide insights into the molecular mechanisms driving APA in cancer and suggest therapeutic strategies.

Beyond mRNA degradation: A new role of YTHDF2 in translation

In this issue of Molecular Cell, Liu et al.

The RNA-stability-independent role of the RNA m6A reader YTHDF2 in promoting protein translation to confer tumor chemotherapy resistance

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Targeting PRDX6-dependent localization and function of GPX4 enhances ferroptosis-mediated tumor suppression

Inducing lipid peroxidation-dependent ferroptosis is a promising anticancer strategy; however, the development of resistance poses a considerable challenge. This study identifies peroxiredoxin 6 (PRDX6) as a crucial modulator of glutathione peroxidase 4 (GPX4), affecting its localization and functional roles, thus contributing to ferroptosis resistance. PRDX6, endowed with phospholipase A2 activity, catalyzes the conversion of peroxy-phospholipids to lysophospholipids and oxidized fatty acids. Through targeted structural mutations and biochemical analyses, we demonstrate that PRDX6 binds to GPX4 via a C47 disulfide bond, facilitating GPX4's membrane translocation and enhanced production of hydroxy fatty acids. Combining the inhibition of PRDX6 with ferroptosis inducers increases lipid peroxidation, effectively suppressing tumor growth in liver and ovarian cancer mouse models, including patient-derived models. Furthermore, high PRDX6 expression correlates with shorter progression-free survival across multiple human cancer types. Collectively, our findings delineate a PRDX6-dependent mechanism in ferroptosis defense, offering new perspectives for targeted cancer therapy.

A multi-omic single-cell landscape of human gynecologic malignancies.

Deconvolution of regulatory mechanisms that drive transcriptional programs in cancer cells is key to understanding tumor biology. Herein, we present matched transcriptome (scRNA-seq) and chromatin accessibility (scATAC-seq) profiles at single-cell resolution from human ovarian and endometrial tumors processed immediately following surgical resection. This dataset reveals the complex cellular heterogeneity of these tumors and enabled us to quantitatively link variation in chromatin accessibility to gene expression. We show that malignant cells acquire previously unannotated regulatory elements to drive hallmark cancer pathways. Moreover, malignant cells from within the same patients show substantial variation in chromatin accessibility linked to transcriptional output, highlighting the importance of intratumoral heterogeneity. Finally, we infer the malignant cell type-specific activity of transcription factors. By defining the regulatory logic of cancer cells, this work reveals an important reliance on oncogenic regulatory elements and highlights the ability of matched scRNA-seq/scATAC-seq to uncover clinically relevant mechanisms of tumorigenesis in gynecologic cancers.