LncRNAs divide and rule: The master regulators of phase separation

Pivotal functions and impact of long con-coding RNAs on cellular processes and genome integrity

Recent advances in uncovering the mysteries of the human genome suggest that long non-coding RNAs (lncRNAs) are important regulatory components. Although lncRNAs are known to affect gene transcription, their mechanisms and biological implications are still unclear. Experimental research has shown that lncRNA synthesis, subcellular localization, and interactions with macromolecules like DNA, other RNAs, or proteins can all have an impact on gene expression in various biological processes. In this review, we highlight and discuss the major mechanisms through which lncRNAs function as master regulators of the human genome. Specifically, the objective of our review is to examine how lncRNAs regulate different processes like cell division, cell cycle, and immune responses, and unravel their roles in maintaining genomic architecture and integrity.

Natural antisense transcripts as versatile regulators of gene expression

Long non-coding RNAs (lncRNAs) are emerging as a major class of gene products that have central roles in cell and developmental biology. Natural antisense transcripts (NATs) are an important subset of lncRNAs that are expressed from the opposite strand of protein-coding and non-coding genes and are a genome-wide phenomenon in both eukaryotes and prokaryotes. In eukaryotes, a myriad of NATs participate in regulatory pathways that affect expression of their cognate sense genes. Recent developments in the study of NATs and lncRNAs and large-scale sequencing and bioinformatics projects suggest that whether NATs regulate expression, splicing, stability or translation of the sense transcript is influenced by the pattern and degrees of overlap between the sense-antisense pair. Moreover, epigenetic gene regulatory mechanisms prevail in somatic cells whereas mechanisms dependent on the formation of double-stranded RNA intermediates are prevalent in germ cells. The modulating effects of NATs on sense transcript expression make NATs rational targets for therapeutic interventions.

Targeting and engineering long non-coding RNAs for cancer therapy

RNA therapeutics (RNATx) aim to treat diseases, including cancer, by targeting or employing RNA molecules for therapeutic purposes. Amongst the most promising targets are long non-coding RNAs (lncRNAs), which regulate oncogenic molecular networks in a cell type-restricted manner. lncRNAs are distinct from protein-coding genes in important ways that increase their therapeutic potential yet also present hurdles to conventional clinical development. Advances in genome editing, oligonucleotide chemistry, multi-omics and RNA engineering are paving the way for efficient and cost-effective lncRNA-focused drug discovery pipelines. In this Review, we present the emerging field of lncRNA therapeutics for oncology, with emphasis on the unique strengths and challenges of lncRNAs within the broader RNATx framework. We outline the necessary steps for lncRNA therapeutics to deliver effective, durable, tolerable and personalized treatments for cancer.

Loss of NAT10 disrupts enhancer organization via p300 mislocalization and suppresses transcription of genes necessary for metastasis progression

Acetylation of protein and RNA represent a critical event for development and cancer progression. NAT10 is the only known RNA acetylase that catalyzes the N4-actylcytidine (ac4C) modification of RNAs. Here, we show that the loss of NAT10 significantly decreases lung metastasis in allograft and genetically engineered mouse models of breast cancer. NAT10 interacts with a mechanosensitive, metastasis susceptibility protein complex at the nuclear pore. In addition to its canonical role in RNA acetylation, we find that NAT10 interacts with p300 at gene enhancers. NAT10 loss is associated with p300 mislocalization into heterochromatin regions. NAT10 depletion disrupts enhancer organization, leading to alteration of gene transcription necessary for metastatic progression, including reduced myeloid cell-recruiting chemokines that results in a less metastasis-prone tumor microenvironment. Our study uncovers a distinct role of NAT10 in enhancer organization of metastatic tumor cells and suggests its involvement in the tumor-immune crosstalk dictating metastatic outcomes.

[Research Progress in the Role of Liquid-Liquid Phase Separation in Human Cancer]

Liquid-liquid phase separation (LLPS) is a reversible process, during which biological macromolecules, including proteins and nucleic acids, condense into liquid membraneless organelles under the influence of weak multivalent interactions. Currently, fluorescence recovery after photobleaching is the primary method used to detect the phase separation of biological macromolecules. Recent studies have revealed the link between abnormal LLPS and the pathogenesis and development of various human cancers. Through phase separation or abnormal phase separation, tumor-related biological macromolecules, such as mRNA, long noncoding RNAs (lncRNAs), and tumor-related proteins, can affect transcriptional translation and DNA damage repair, regulate the autophagy and ferroptosis functions of cells, and thus regulate the development of various tumors. In this review, we summarized the latest research findings on the mechanism of LLPS in the pathogenesis and progression of tumors and elaborated on the promotion or inhibition of autophagy, tumor immunity, DNA damage repair, and cell ferroptosis after abnormal phase separation of biomolecules, including mRNA, lncRNA, and proteins, which subsequently affects the pathogenesis and progression of tumors. According to published findings, many biological macromolecules can regulate transcriptional translation, expression, post-transcriptional modification, cell signal transduction, and other biological processes through phase separation. Therefore, further expansion of the research field of phase separation and in-depth investigation of its molecular mechanisms and regulatory processes hold extensive research potential.

Vinorelbine Alters lncRNA Expression in Association with EGFR Mutational Status and Potentiates Tumor Progression Depending on NSCLC Cell Lines' Genetic Profile

Lung cancer remains the leading cause of cancer-related mortality worldwide, with non-small cell lung cancer (NSCLC) as the most common type. In addition, NSCLC has a high mortality rate and an overall adverse patient outcome. Although significant improvements have been made in therapeutic options, effectiveness is still limited in late stages, so the need for a better understanding of the genomics events underlying the current therapies is crucial to aid future drug development. Vinorelbine (VRB) is an anti-mitotic chemotherapy drug (third-generation vinca alkaloid) used to treat several malignancies, including NSCLC. However, despite its widespread clinical use, very little is known about VRB-associated genomic alterations in different subtypes of NSCLC. This article is an in vitro investigation of the cytotoxic effects of VRB on three different types of NSCLC cell lines, A549, Calu-6, and H1792, with a closer focus on post-treatment genetic alterations. Based on the obtained results, VRB cytotoxicity produces modifications on a cellular level, altering biological processes such as apoptosis, autophagy, cellular motility, cellular adhesion, and cell cycle, but also at a genomic level, dysregulating the expression of some coding genes, such as EGFR, and long non-coding RNAs (lncRNAs), including CCAT1, CCAT2, GAS5, MALAT1, NEAT1, NORAD, XIST, and HOTAIR, that are implicated in the mitogen-activated protein kinase (MAPK) signaling pathway. Therefore, although extensive validation is required, these results pave the way towards a better understanding of the cellular and genomic alterations underlying the cytotoxicity of VRB.

Unconventional roles of chromatin remodelers and long non-coding RNAs in cell division

The aim of this review article is to focus on the unconventional roles of epigenetic players (chromatin remodelers and long non-coding RNAs) in cell division, beyond their well-characterized functions in chromatin regulation during cell differentiation and development. In the last two  decades, diverse experimental evidence has shown that subunits of SRCAP and p400/TIP60 chromatin remodeling complexes in humans relocate from interphase nuclei to centrosomes, spindle or midbody, with their depletion yielding an array of aberrant outcomes of mitosis and cytokinesis. Remarkably, this behavior is shared by orthologous subunits of the Drosophila melanogaster DOM/TIP60 complex, despite fruit flies and humans diverged over 700 million years ago. In short, the available data support the view that subunits of these complexes are a new class of moonlighting proteins, in that they lead a "double life": during the interphase, they function in chromatin regulation within the nucleus, but as the cell progresses through mitosis, they interact with established mitotic factors, thus becoming integral components of the cell division apparatus.  By doing so, they contribute to ensuring the correct distribution of chromosomes in the two daughter cells and, when dysfunctional, can cause genomic instability, a condition that can trigger tumorigenesis and developmental diseases. Research over the past few years has unveiled a major contribution of long non-coding RNAs (lncRNAs) in the epigenetics regulation of gene expression which also impacts on cell division control. Here, we focus on possible structural roles of lncRNAs in the execution of cytokinesis: in particular, we suggest that specific classes of lncRNAs relocate to the midbody to form an architectural scaffold ensuring its proper assembly and function during abscission. Drawing attention to experimental evidence for non-canonical extranuclear roles of chromatin factors and lncRNAs has direct implications on important and novel aspects concerning both the epigenetic regulation and the evolutionary dynamics of cell division with a significant impact on differentiation, development, and diseases.

Tracking the Message: Applying Single Molecule Localization Microscopy to Cellular RNA Imaging

RNA function is increasingly appreciated to be more complex than merely communicating between DNA sequence and protein structure. RNA localization has emerged as a key contributor to the intricate roles RNA plays in the cell, and the link between dysregulated spatiotemporal localization and disease warrants an exploration beyond sequence and structure. However, the tools needed to visualize RNA with precise resolution are lacking in comparison to methods available for studying proteins. In the past decade, many techniques have been developed for imaging RNA, and in parallel super resolution and single-molecule techniques have enabled imaging of single molecules in cells. Of these methods, single molecule localization microscopy (SMLM) has shown significant promise for probing RNA localization. In this review, we highlight current approaches that allow super resolution imaging of specific RNA transcripts and summarize challenges and future opportunities for developing innovative RNA labeling methods that leverage the power of SMLM.

Liquid-liquid phase separation of protein tau: An emerging process in Alzheimer's disease pathogenesis

Metabolic reactions within cells occur in various isolated compartments with or without borders, the latter being known as membrane-less organelles (MLOs). The MLOs show liquid-like properties and are formed by a process known as liquid-liquid phase separation (LLPS). MLOs contribute to different molecules interactions such as protein-protein, protein-RNA, and RNA-RNA driven by various factors, such as multivalency of intrinsic disorders. MLOs are involved in several cell signaling pathways such as transcription, immune response, and cellular organization. However, disruption of these processes has been found in different pathologies. Recently, it has been demonstrated that protein aggregates, a characteristic of some neurodegenerative diseases, undergo similar phase separation. Tau protein is known as a major neurofibrillary tangles component in Alzheimer's disease (AD). This protein can undergo phase separation to form a MLO known as tau droplet in vitro and in vivo, and this process can be facilitated by several factors, including crowding agents, RNA, and phosphorylation. Tau droplet has been shown to mature into insoluble aggregates suggesting that this process may precede and induce neurodegeneration in AD. Here we review major factors involved in liquid droplet formation within a cell. Additionally, we highlight recent findings concerning tau aggregation following phase separation in AD, along with the potential therapeutic strategies that could be explored in this process against the progression of this pathology.

LncRNA PTOV1-AS2 Promotes Colon Cancer Progression through the miR-145-5p/FSCN1 Axis

Objective

The long noncoding RNA (lncRNA) gene PTOV1-AS2 is a potentially oncogenic lncRNA gene. However, its role and regulatory mechanism in the occurrence and development of colon cancer are still unclear. In this study, the lncRNA PTOV1-AS2 was used as a starting point to investigate the role of competing endogenous RNA (ceRNA) regulatory mechanisms in colon cancer.

Methods

The expression of lncRNA PTOV1-AS2 mRNA in colon cancer tissues and cell lines was measured by quantitative real-time polymerase chain reaction (qRT-PCR) and screened for differential expression in cells. We examined the effects of lncRNA PTOV1-AS2 overexpression or downregulation of its expression on various cellular processes in HCT116 and SW620 cells after the transfection with an overexpression construct or PTOV1-AS2p-specific shRNA, respectively. In particular, we examined the effects on cell proliferation, migration, and invasion using the cell counting kit-8 CCK-8 assay and Transwell migration and invasion assays, respectively. In addition, the binding targets of lncRNA PTOV1-AS2/miR-145-5p and miR-145-5p/FSCN1 were predicted using various bioinformatics tools and validated by a dual luciferase assay. We also examined the effect of the lncRNA PTOV1-AS2/miR-145-5p axis on FSCN1 expression by qRT-PCR analysis. Furthermore, we investigated the effect of the PTOV1-AS2/miR-145-5p/FSCN1 axis on the biological function of colon cancer cells using an in vitro colon cancer cell model with reduced expression of PTOV1-AS2 and simultaneous transfection of a miR-145-5p inhibitor or FSCN1 vector. Additionally, we established a colon cancer xenograft tumor nude mouse model and used it to investigate the effect of locally injected lncRNA PTOV1-AS2 vector on the tumor growth and survival status of tumor-bearing mice.

Results

We found that PTOV1-AS2 was highly expressed in colon cancer, which was associated with worse survival. High expression of PTOV1-AS2 promoted cell proliferation, migration, and invasion, while low expression of PTOV1-AS2 inhibited these processes in HCT116 and SW620 cells. The microRNA miR-145-5p was found to bind to the 3'-UTR region of both PTOV1-AS2 and FSCN1. In addition, miR-145-5p decreased the protein expression of its target gene FSCN1 and reduced the PTOV1-AS2-induced expression of FSCN1 in colon cancer cell lines. Also, silencing miR-145-5p or enhancing FSCN1 expression could partially restore the inhibition of cell proliferation, migration, invasion, and the tumorigenic capacity caused by silencing the expression of PTOV1-AS2 in vitro and in vivo.

Conclusion

PTOV1-AS2 promotes colon cancer progression by "sponging" miR-145-5p to upregulate FSCN1.

Innate Immunity in Cardiovascular Diseases-Identification of Novel Molecular Players and Targets

During the past few years, unexpected developments have driven studies in the field of clinical immunology. One driver of immense impact was the outbreak of a pandemic caused by the novel virus SARS-CoV-2. Excellent recent reviews address diverse aspects of immunological re-search into cardiovascular diseases. Here, we specifically focus on selected studies taking advantage of advanced state-of-the-art molecular genetic methods ranging from genome-wide epi/transcriptome mapping and variant scanning to optogenetics and chemogenetics. First, we discuss the emerging clinical relevance of advanced diagnostics for cardiovascular diseases, including those associated with COVID-19-with a focus on the role of inflammation in cardiomyopathies and arrhythmias. Second, we consider newly identified immunological interactions at organ and system levels which affect cardiovascular pathogenesis. Thus, studies into immune influences arising from the intestinal system are moving towards therapeutic exploitation. Further, powerful new research tools have enabled novel insight into brain-immune system interactions at unprecedented resolution. This latter line of investigation emphasizes the strength of influence of emotional stress-acting through defined brain regions-upon viral and cardiovascular disorders. Several challenges need to be overcome before the full impact of these far-reaching new findings will hit the clinical arena.

LINC02323 facilitates development of lung squamous cell carcinoma by miRNA sponge and RBP dysregulation and links to poor prognosis

BACKGROUND

The poor outcome of patients with lung squamous cell carcinoma (LUSC) highlights the importance of the identification of novel effective prognostic markers and therapeutic targets. Long noncoding RNAs (lncRNAs) have generally been considered to serve important roles in tumorigenesis and the development of various types of cancer, including LUSC.

METHODS

Here, we aimed to investigate the role of LINC02323 in LUSC and its potential mechanisms by performing comprehensive bioinformatic analyses.

RESULTS

LINC02323 was elevated and positively associated with unfavorable prognosis of LUSC patients. LINC02323 exerted oncogenic function by competitively binding to miR-1343-3p and miR-6783-3p, thereby upregulating L1CAM expression. Indeed, we also determined that LINC02323 could interact with the RNA-binding protein DDX3X, which regulates various stages of RNA expression and processing.

CONCLUSION

Taken together, we identified that LINC02323 and its indirect target L1CAM can act as novel biomarkers for determining the prognosis of patients with LUSC and thus deserves further study.

Catalytic RNA Oligomers Formed by Co-Oligomerization of a Pair of Bimolecular RNase P Ribozymes

Naturally occurring ribozymes with a modular architecture are promising platforms for construction of RNA nanostructures because modular redesign enables their oligomerization. The resulting RNA nanostructures can exhibit the catalytic function of the parent ribozyme in an assembly dependent manner. In this study, we designed and constructed open-form oligomers of a bimolecular form of an RNase P ribozyme. The ribozyme oligomers were analyzed biochemically and by atomic force microscopy (AFM).