Biology subjects

Yen, L.

Publications and source records attributed to Yen, L..

4 recordsLinked to original sources

bioRxiv2023

pA regulator: a system for controlling mammalian gene expression via the modulation of polyA signal cleavage

The ability to control the expression of a therapeutic gene or a transgene in mammalian cells is crucial for safe and efficacious gene and cell therapy, as well as for elucidating the function of a specific gene product. Yet current mammalian gene regulation systems either evoke harmful immune responses in hosts or lack the required regulatory efficiency. Here we describe a highly responsive RNA-based molecular switch, the pA regulator, that harnesses the power of polyA signal cleavage within the 5 UTR to control mammalian gene expression. The pA regulator is governed by a dual mechanism to ensure maximal control of gene expression: (1) aptamer clamping of polyA signal via drug binding and (2) drug-induced alternative splicing that removes the polyA signal. The metholology achieves an induction efficiency up to 900-fold with an EC50 of 0.5g/ml Tetracycline, a drug concentration that falls well within the FDA-approved dose range. The pA regulator circumvents the immune responses that plague other systems by eliminating the use of a regulatory foreign protein and the need to change transgene coding sequences. Furthermore, it is not dependent on any specific promoter, therefore the system is simple to implement in a single non-viral or viral vector. In a mouse study using AAV-mediated gene transfer, we showed that the pA regulator controlled transgene expression in a "dose-dependent and "reversible" manner and exhibited long-term stability in vivo, in which both features are crucial for effective therapeutics. The pA regulator is the first non-immunogenic system that demonstrates an EC50 at a drug concentration approved by FDA, making it a clinically relevant gene regulation system that could open a new window of opportunity in clinical applications as well as biological studies.

synthetic biology↗

bioRxiv2019

Genome-wide, integrative analysis implicates circular RNA dysregulation in autism and the corresponding circular RNA-microRNA-mRNA regulatory axes

Circular RNAs (circRNAs), a class of long non-coding RNAs, are known to be enriched in mammalian brain and neural tissues. While the effects of regulatory genetic variants on gene expression in autism spectrum disorder (ASD) have been widely reported, the role of circRNAs in ASD remains largely unknown. Here, we performed genome-wide circRNA expression profiling in post-mortem brains from individuals with ASD and controls and identified 60 circRNAs and three co-regulated modules that were perturbed in ASD. By integrating circRNA, microRNA, and mRNA dysregulation data derived from the same cortex samples, we identified 8,170 ASD-associated circRNA-microRNA-mRNA interactions. Putative targets of the axes were enriched for ASD risk genes and genes encoding inhibitory postsynaptic density (PSD) proteins, but not for genes implicated in monogenetic forms of other brain disorders or genes encoding excitatory PSD proteins. This result reflects the previous observation that ASD-derived organoids exhibit overproduction of inhibitory neurons. We further confirmed that some ASD risk genes (NLGN1, STAG1, HSD11B1, VIP, and UBA6) were indeed regulated by an upregulated circRNA (circARID1A) via sponging a downregulated microRNA (miR-204-3p) in human neuronal cells. We provided a systems-level view of landscape of circRNA regulatory networks in ASD cortex samples. We also provided multiple lines of evidence for the functional role of ASD for circRNA dysregulation and a rich set of ASD-associated circRNA candidates and the corresponding circRNA-miRNA-mRNA axes, particularly those involving ASD risk genes. Our findings thus support a role for circRNA dysregulation and the corresponding circRNA-microRNA-mRNA axes in ASD pathophysiology.

bioinformatics↗

bioRxiv2018

The Histone H3-H4 Tetramer is a Copper Reductase Enzyme

Ancestral histones were present in organisms with small genomes, no nucleus, and little evidence for epigenetic regulation, suggesting histones may have additional older functions. We report that the histone H3-H4 tetramer is an enzyme that catalyzes the reduction of Cu2+ to Cu1+ when assembled in vitro from recombinant histones. Mutations of residues in the putative active site at the interface of the apposing H3 proteins alter the enzymatic activity and cellular processes such as Sod1 function or mitochondrial respiration that depend on availability of reduced copper. These effects are not due to altered gene expression or copper abundance but are consistent with decreased levels of cuprous ions. We propose that the H3-H4 tetramer is an oxidoreductase that provides biousable copper for cellular and mitochondrial chemistry. As the emergence of eukaryotes coincided with the Great Oxidation Event and decreased biousability of metals, the histone enzymatic function may have facilitated eukaryogenesis.

molecular biology↗

bioRxiv2017

RNA-mediated Genomic Arrangements in Mammalian Cells

One of the hallmarks of cancer is the formation of oncogenic fusion genes as a result of chromosomal translocations. Fusion genes are presumed to occur prior to fusion RNA expression. However, studies have reported the presence of fusion RNAs in individuals who were negative for chromosomal translocations. These observations give rise to \"the cart before the horse\" hypothesis, in which fusion RNA precedes the fusion gene and guides the genomic rearrangements that ultimately result in gene fusions. Yet RNA-mediated genomic rearrangement in mammalian cells has never been demonstrated. Here we provide evidence that expression of a chimeric RNA drives formation of a specified gene fusion via genomic rearrangement in mammalian cells. The process is (1) specified by the sequence of chimeric RNA involved, (2) facilitated by physiological hormone levels, (3) permissible regardless of intra-chromosomal (TMPRSS2-ERG) or inter-chromosomal (TMPRSS2-ETV1) fusion, and (4) can occur in normal cells prior to malignant transformation. We demonstrate that, contrary to \"the cart before the horse\" model, it is the antisense rather than sense chimeric RNAs that effectively drive gene fusion, and that this disparity can be explained by transcriptional conflict. Furthermore, we identified an endogenous RNA AZI1 that acts as the initiator RNA to induce TMPRSS2-ERG fusion. RNA-driven gene fusion demonstrated in this report provides important insight in early disease mechanism, and could have fundamental implications in the biology of mammalian genome stability, as well as gene editing technology via mechanisms native to mammalian cells.

cancer biology↗