Biology subjects

Tano, V.

Publications and source records attributed to Tano, V..

5 recordsLinked to original sources

bioRxiv2026

Intron 13 retention expands the ADAR1 isoform repertoire to rewire PKR signaling and promote tumorigenesis

For decades, the biology of ADAR1 has been framed around two major isoforms: the nuclear-enriched p110 and the predominantly cytoplasmic p150. Here, we reveal an unexpected repertoire expansion of ADAR1 isoforms that is driven by intron retention. Specifically, intron 13 (I13) can be retained in ADAR1 transcripts, conferred by an evolutionarily conserved weaker 5SS. In addition, we found that the I13 retention (I13R) is negatively autoregulated by ADAR1 through antagonizing the binding of hnRNPA1 to I13 in an editing-independent manner. Despite being sensitive to nonsense-mediated decay, I13R generates two previously uncharacterized truncated isoforms - p90 and p130, that both lack the C-terminal portion of the deaminase domain. Intriguingly, ADAR1p90 - a derivative of the canonical nuclear-enriched p110 isoform - is predominantly cytoplasmic, that effectively represses PKR and eIF2 activation through the sequestration of immunogenic double-stranded RNA (dsRNA) substrates. Furthermore, in a colorectal cancer (CRC) cohort, p90 levels are increased in most tumors relative to matched normal tissues that positively correlates with hnRNPA1 expression. Functionally, xenografts expressing ADAR1p90 grow significantly faster and larger than those expressing ADAR1p110, indicating enhanced tumorigenic potential. These findings revise the canonical view of ADAR1 isoforms, demonstrating that intron retention can generate alternative isoforms with augmented functions that tumors readily exploit. One Sentence SummaryThe conserved retention of I13 in ADAR1 transcripts gives rise to previously uncharacterized C-terminal truncated cytoplasmic ADAR1 isoforms, p90 and p130, which, although devoid of catalytic activity, sequester immunogenic dsRNA substrates, thereby preventing PKR binding and downstream activation of eIF2.

cell biology↗

bioRxiv2026

Mitochondrial dsRNA: A Hidden Source of Immunogenic RNA in ADAR1 Deficiency

Double-stranded RNA (dsRNA) triggers immune responses during viral infections, but self-derived dsRNA can activate similar pathways. To prevent this, the body relies on mechanisms like ADAR1, an RNA-editing enzyme essential for immune regulation. Dysfunction of ADAR1 is linked to various diseases, yet the nature and role of dsRNAs accumulating in its absence remain unclear. Here, we identify mitochondrial dsRNA (mt-dsRNA), transcribed from the mitochondrial genome, as a major contributor to the endogenous dsRNA pool in ADAR1-deficient human and murine cells. We propose a "Draw-and-Release" model, where ADAR1 loss increases mitochondrial reactive oxygen species (mtROS), causing mt-dsRNA accumulation in the mitochondrial matrix ("Draw" phase) and its immune-activating release into the cytosol upon mitochondrial protein dysfunction ("Release" phase). This study highlights the importance of mitochondrial integrity in mitigating ADAR1-related pathologies.

cell biology↗

bioRxiv2024

PRMT5 is required for full-length HTT expression by repressing multiple proximal intronic polyadenylation sites

Expansion of the CAG trinucleotide repeat tract in exon 1 of the Huntingtin (HTT) gene above a threshold of [~]36 repeats causes Huntingtons disease (HD) through the expression of a polyglutamine-expanded form of the HTT protein. This mutation triggers wide-ranging cellular and biochemical pathologies leading to cognitive, motor, and psychiatric symptoms in HD patients. As accurate splicing is required to produce the full-length HTT protein of [~]348 kDa, targeting HTT splicing with small molecule drugs is a compelling approach to lower HTT protein levels to treat HD, and splice modulators are being tested in the clinic. Here, we identify PRMT5 as a novel regulator of HTT mRNA splicing and alternative polyadenylation. PRMT5 inhibition disrupts the splicing of HTT introns 9 and 10, leading to activation of multiple proximal intronic polyadenylation sites within these introns and promoting premature termination, cleavage and polyadenylation (PCPA) of the HTT mRNA, thus lowering total HTT protein levels. We also detected increasing levels of these truncated, intron-containing HTT transcripts across a series of neuronal differentiation samples which correlated with lower PRMT5 expression. Notably, PRMT5 inhibition in glioblastoma (GBM) stem cells potently induced neuronal differentiation. We posit that PRMT5-mediated regulation of intronic polyadenylation, premature termination and cleavage of the HTT mRNA modulates HTT expression and plays an important role during embryonic development and neuronal differentiation.

neuroscience↗

bioRxiv2022

Widespread dysregulation of mRNA splicing implicates RNA processing in the development and progression of Huntington's disease

In Huntingtons disease (HD), a CAG repeat expansion mutation in the HTT gene drives a gain-of-function toxicity that disrupts mRNA processing. Although widespread dysregulation of gene splicing in the striatum has been shown in human HD post-mortem brain tissue, post-mortem analyses are likely confounded by cell type composition changes due to neuronal loss and astrogliosis in late stage HD. This limits the ability to identify dysregulation related to early pathogenesis. To study alternative splicing changes in early HD, we performed RNA-sequencing analysis in an established isogenic HD neuronal cell model. We report cell type-associated and CAG length-dependent splicing changes, and find an enrichment of RNA processing genes coupled with neuronal function-related genes showing mutant HTT-associated splicing changes. Comparison with post-mortem data also identified splicing events associated with early pathogenesis that persist to later stages of disease. In summary, our results highlight splicing dysregulation in RNA processing genes in early and late-stage HD, which may lead to disrupted neuronal function and neuropathology.

neuroscience↗

bioRxiv2022

Human endogenous retrovirus activation contributes to biliary atresia pathogenesis through re-education of resident macrophages

Biliary atresia (BA) is a life-threatening neonatal fibro-inflammatory disease characterized by hepatic fibrosis, cirrhosis, and end-stage liver failure. BA is also the most frequent indication of pediatric liver transplantation globally. Despite the devastating condition of BA, the pathogenesis mechanism is unknown. Viral infection has been suggested to be associated with BA, but definitive evidence to support this hypothesis is not available. To elucidate the virus-associated pathogenesis mechanism of BA and to understand the immune ecosystem, we performed single-cell transcriptomic and proteomic profiling of BA livers. We detected human endogenous virus (HERV) in infants with BA and their parents. HERV was mainly found in FOLR2+ resident macrophages, T cells, and NK cells. In addition, HERV activation re-educated the fetal-derived FOLR2+ resident macrophages, and reactive oxygen species scavenging neutrophil recruitment was impaired in patients with BA and HERV+, due to FOLR2+ resident macrophage re-education. Furthermore, we showed depletion of FOLR2+ resident macrophage and N-acetylcysteine treatment could rescue the liver damage in BA. Overall, our study revealed the HERV-associated immunopathology mechanism of BA. These results contribute to potential diagnosis and immunotherapy strategies for BA.

pathology↗