Biomolecular Condensation: A New Phase in Cancer Research

Mechanistic insights into DXO1 and XRN3: regulatory roles of RNA stability, transcription, and liquid-liquid phase separation in Arabidopsis thaliana (L.) Heynh

The regulation of RNA stability and transcription in eukaryotic organisms is a sophisticated process involving various complex mechanisms. This paper explores the regulatory functions of DXO1 and XRN3 proteins in RNA stability and transcription in the model plant Arabidopsis thaliana (L.) Heynh. DXO1 is noted for its roles in mRNA 5'-end quality control, removal of non-canonical NAD+ caps, and activation of RNA guanosine-7 methyltransferase. In contrast, XRN3 ensures RNA integrity through precise degradation. While current studies have identified various termination regions across genes influenced by XRN3, advanced RNA sequencing techniques have revealed that XRN3-mediated changes in gene expression often result from siRNA production, leading to gene silencing rather than direct effects on transcription termination. This review emphasizes the need to further explore the DXO1-XRN3 axis, their interactive mechanisms, and their potential involvement in liquid-liquid phase separation (LLPS) during transcription. It further suggests evaluating XRN proteins like XRN4 to assess potential redundancies in RNA degradation pathways. The advent of PSPredictor, a tool for identifying LLPS proteins, along with protein function prediction techniques, promises to advance our understanding of DXO1 and XRN3 in maintaining RNA equilibrium and the dynamics of LLPS in plant biology. The review concludes by calling for more studies on the plant-specific roles of the DXO1 N-terminal extension (NTE), predictive tools for LLPS-forming proteins, and the interplay of RNA Pol II CTD code modulation by transcription factors to enhance knowledge of plant stress adaptation and improve agricultural productivity.

Unveiling the Complexity of cis-Regulation Mechanisms in Kinases: A Comprehensive Analysis

Protein cis-regulatory elements (CREs) are regions that modulate the activity of a protein through intramolecular interactions. Kinases, pivotal enzymes in numerous biological processes, often undergo regulatory control via inhibitory interactions in cis. This study delves into the mechanisms of cis regulation in kinases mediated by CREs, employing a combined structural and sequence analysis. To accomplish this, we curated an extensive dataset of kinases featuring annotated CREs, organized into homolog families through multiple sequence alignments. Key molecular attributes, including disorder and secondary structure content, active and ATP-binding sites, post-translational modifications, and disease-associated mutations, were systematically mapped onto all sequences. Additionally, we explored the potential for conformational changes between active and inactive states. Finally, we explored the presence of these kinases within membraneless organelles and elucidated their functional roles therein. CREs display a continuum of structures, ranging from short disordered stretches to fully folded domains. The adaptability demonstrated by CREs in achieving the common goal of kinase inhibition spans from direct autoinhibitory interaction with the active site within the kinase domain, to CREs binding to an alternative site, inducing allosteric regulation revealing distinct types of inhibitory mechanisms, which we exemplify by archetypical representative systems. While this study provides a systematic approach to comprehend kinase CREs, further experimental investigations are imperative to unravel the complexity within distinct kinase families. The insights gleaned from this research lay the foundation for future studies aiming to decipher the molecular basis of kinase dysregulation, and explore potential therapeutic interventions.

8q24 derived ZNF252P promotes tumorigenesis by driving phase separation to activate c-Myc mediated feedback loop

As a well-known cancer risk region, the 8q24 locus is frequently amplified in a variety of solid tumors. Here we identify a pseudogene-derived oncogenic lncRNA, ZNF252P, which is upregulated in a variety of cancer types by copy number gain as well as c-Myc-mediated transcriptional activation. Mechanistically, ZNF252P binds and drives "phase separation" of HNRNPK and ILF3 protein in the nucleus and cytoplasm, respectively, to transcriptionally and posttranscriptionally activate c-Myc, thus forming a c-Myc/ZNF252P/c-Myc positive feedback loop. These findings expand the understanding of the relationship between genomic instability in the 8q24 region and tumorigenesis and clarify a regulatory mechanism involved in transcription and posttranscription from the perspective of RNA-mediated nuclear and cytoplasmic protein phase separation, which sheds light on the dialogue with the driver oncogene c-Myc. The pivotal regulatory axis of ZNF252P/c-Myc has potential as a promising biomarker and therapeutic target in cancer development.

Targeting FOXM1 condensates reduces breast tumour growth and metastasis

Identifying phase-separated structures remains challenging, and effective intervention methods are currently lacking1. Here we screened for phase-separated proteins in breast tumour cells and identified forkhead (FKH) box protein M1 (FOXM1) as the most prominent candidate. Oncogenic FOXM1 underwent liquid-liquid phase separation (LLPS) with FKH consensus DNA element, and compartmentalized the transcription apparatus in the nucleus, thereby sustaining chromatin accessibility and super-enhancer landscapes crucial for tumour metastatic outgrowth. Screening an epigenetics compound library identified AMPK agonists as suppressors of FOXM1 condensation. AMPK phosphorylated FOXM1 in the intrinsically disordered region (IDR), perturbing condensates, reducing oncogenic transcription, accumulating double-stranded DNA to stimulate innate immune responses, and endowing discrete FOXM1 with the ability to activate immunogenicity-related gene expressions. By developing a genetic code-expansion orthogonal system, we demonstrated that a phosphoryl moiety at a specific IDR1 site causes electrostatic repulsion, thereby abolishing FOXM1 LLPS and aggregation. A peptide targeting IDR1 and carrying the AMPK-phosphorylated residue was designed to disrupt FOXM1 LLPS and was shown to inhibit tumour malignancy, rescue tumour immunogenicity and improve tumour immunotherapy. Together, these findings provide novel and in-depth insights on function and mechanism of FOXM1 and develop methodologies that hold promising implications in clinics.

The MTR4/hnRNPK complex surveils aberrant polyadenylated RNAs with multiple exons

RNA surveillance systems degrade aberrant RNAs that result from defective transcriptional termination, splicing, and polyadenylation. Defective RNAs in the nucleus are recognized by RNA-binding proteins and MTR4, and are degraded by the RNA exosome complex. Here, we detect aberrant RNAs in MTR4-depleted cells using long-read direct RNA sequencing and 3' sequencing. MTR4 destabilizes intronic polyadenylated transcripts generated by transcriptional read-through over one or more exons, termed 3' eXtended Transcripts (3XTs). MTR4 also associates with hnRNPK, which recognizes 3XTs with multiple exons. Moreover, the aberrant protein translated from KCTD13 3XT is a target of the hnRNPK-MTR4-RNA exosome pathway and forms aberrant condensates, which we name KCTD13 3eXtended Transcript-derived protein (KeXT) bodies. Our results suggest that RNA surveillance in human cells inhibits the formation of condensates of a defective polyadenylated transcript-derived protein.

Emerging roles of liquid-liquid phase separation in liver innate immunity

Biomolecular condensates formed by liquid-liquid phase separation (LLPS) have become an extensive mechanism of macromolecular metabolism and biochemical reactions in cells. Large molecules like proteins and nucleic acids will spontaneously aggregate and assemble into droplet-like structures driven by LLPS when the physical and chemical properties of cells are altered. LLPS provides a mature molecular platform for innate immune response, which tightly regulates key signaling in liver immune response spatially and physically, including DNA and RNA sensing pathways, inflammasome activation, and autophagy. Take this, LLPS plays a promoting or protecting role in a range of liver diseases, such as viral hepatitis, non-alcoholic fatty liver disease, liver fibrosis, hepatic ischemia-reperfusion injury, autoimmune liver disease, and liver cancer. This review systematically describes the whole landscape of LLPS in liver innate immunity. It will help us to guide a better-personalized approach to LLPS-targeted immunotherapy for liver diseases.

Phase-Separated Biomolecular Condensation in Cancer: New Horizons and Next Frontiers

SUMMARY

Beyond lipid membrane compartments, cells including cancer cells utilize various membraneless compartments, often termed biomolecular condensates, to regulate or organize key cellular processes underlying physiologic or pathologic phenotypes. In this commentary, the emergence of biomolecular condensation in cancer biology is highlighted, with a focus on key unanswered questions and with implications for improving the understanding of cancer pathogenesis and developing innovative cancer management strategies.

Targeting Biomolecular Condensation and Protein Aggregation against Cancer

Biomolecular condensates, membrane-less entities arising from liquid-liquid phase separation, hold dichotomous roles in health and disease. Alongside their physiological functions, these condensates can transition to a solid phase, producing amyloid-like structures implicated in degenerative diseases and cancer. This review thoroughly examines the dual nature of biomolecular condensates, spotlighting their role in cancer, particularly concerning the p53 tumor suppressor. Given that over half of the malignant tumors possess mutations in the TP53 gene, this topic carries profound implications for future cancer treatment strategies. Notably, p53 not only misfolds but also forms biomolecular condensates and aggregates analogous to other protein-based amyloids, thus significantly influencing cancer progression through loss-of-function, negative dominance, and gain-of-function pathways. The exact molecular mechanisms underpinning the gain-of-function in mutant p53 remain elusive. However, cofactors like nucleic acids and glycosaminoglycans are known to be critical players in this intersection between diseases. Importantly, we reveal that molecules capable of inhibiting mutant p53 aggregation can curtail tumor proliferation and migration. Hence, targeting phase transitions to solid-like amorphous and amyloid-like states of mutant p53 offers a promising direction for innovative cancer diagnostics and therapeutics.

Protein phase separation: new insights into cell division

As the foundation for the development of multicellular organisms and the self-renewal of single cells, cell division is a highly organized event which segregates cellular components into two daughter cells equally or unequally, thus producing daughters with identical or distinct fates. Liquid-liquid phase separation (LLPS), an emerging biophysical concept, provides a new perspective for us to understand the mechanisms of a wide range of cellular events, including the organization of membrane-less organelles. Recent studies have shown that several key organelles in the cell division process are assembled into membrane-free structures via LLPS of specific proteins. Here, we summarize the regulatory functions of protein phase separation in centrosome maturation, spindle assembly and polarity establishment during cell division.

From the Catastrophic Objective Irreproducibility of Cancer Research and Unavoidable Failures of Molecular Targeted Therapies to the Sparkling Hope of Supramolecular Targeted Strategies

The unprecedented non-reproducibility of the results published in the field of cancer research has recently come under the spotlight. In this short review, we try to highlight some general principles in the organization and evolution of cancerous tumors, which objectively lead to their enormous variability and, consequently, the irreproducibility of the results of their investigation. This heterogeneity is also extremely unfavorable for the effective use of molecularly targeted medicine. Against the seemingly comprehensive background of this heterogeneity, we single out two supramolecular characteristics common to all tumors: the clustered nature of tumor interactions with their microenvironment and the formation of biomolecular condensates with tumor-specific distinctive features. We suggest that these features can form the basis of strategies for tumor-specific supramolecular targeted therapies.