Biology subjects

Gan, T.

Publications and source records attributed to Gan, T..

7 recordsLinked to original sources

bioRxiv2025

Targeting Non-Catalytic Sites of SRC Sensitizes the Efficacy of SRC Kinase Inhibitors in Solid Tumors

The non-receptor tyrosine kinase SRC promotes the progression of hematologic malignancies and numerous solid tumors. Several SRC kinase inhibitors have been approved for the treatment of hematologic malignancies. However, drug resistance to sole ATP pocket-targeted kinase inhibition, coupled with low potency for solid tumors and insufficient selectivity, has limited the clinical application of SRC kinase inhibitors. The non-catalytic functions of kinases have provided crucial mechanisms underlying kinase inhibitor resistance, thereby presenting new opportunities for discovery SRC-targeted strategies. In this study, we discovered that upon abrogation of phosphorylation by SRC kinase inhibitors, non-catalytic SRC promotes the transcription of the oncogenes TRIB3 and SPC24 transcription by binding to their promoter sequence. Simultaneously, it interacts with TRIB3 and prevents their proteasome-mediated degradation by the E3 ligase CHIP, ultimately inducing resistance to SRC kinase inhibitors. The peptide TS1-2, blocking SRC/TRIB3 interaction in non-catalytic regions, inhibits the tumor progression of pancreatic ductal adenocarcinoma (PDAC), kidney renal clear cell carcinoma (KIRC), liver hepatocellular carcinoma (LIHC), and breast invasive carcinoma (BRCA), and enhances the efficacy of SRC kinase inhibitors in solid tumors. This study provides the insights of non-catalytic functions of SRC, validates the tumor-promoting function and mechanism of nuclear accumulation of SRC/TRIB3 following SRC kinase inhibitor treatment, identifies SRC/TRIB3 interaction as a potential non-catalytic target, and offers the candidate peptide TS1-2 as a potential combination strategy for overcoming SRC kinase inhibitor resistance. SignificanceThe scaffolding functions of SRC reduced the efficacy of SRC kinase inhibitors, and targeting SRC/TRIB3 non-catalytic functions synergizes the therapeutic effects of SRC kinase inhibitors in SRC-dependent solid tumors. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=177 SRC="FIGDIR/small/638389v2_ufig1.gif" ALT="Figure 1"> View larger version (55K): org.highwire.dtl.DTLVardef@17aa618org.highwire.dtl.DTLVardef@12e86eeorg.highwire.dtl.DTLVardef@19c8d82org.highwire.dtl.DTLVardef@10e6c46_HPS_FORMAT_FIGEXP M_FIG C_FIG SRC kinase inhibitors block myristoylation-dependent membrane location and catalytic phosphorylation of SRC. Phosphorylated SRC activates STAT1 and thereby represses TRIB3 transcription. Accumulated non-catalytic SRC promotes TRIB3, SPC24 transcription. Upregulated TIRB3 interacts with SRC to reduce CHIP-mediated ubiquitin-proteasomal degradation. The peptide TS1-2 disrupts TRIB3/SRC complex by targeting Non-kinase regions of SRC, consequently enhancing the therapeutic efficacy of SRC kinase inhibitors.

cancer biology↗

bioRxiv2024

Barcoded SARS-CoV-2 viruses define the impact of time and route of transmission on the transmission bottleneck in a Syrian hamster model.

The transmission bottleneck, defined as the number of viruses that transmit from one host to infect another, is an important determinant of the rate of virus evolution and the level of immunity required to protect against virus transmission. Despite its importance, SARS-CoV-2s transmission bottleneck remains poorly characterized, in part due to a lack of quantitative measurement tools. To address this, we adapted a SARS-CoV-2 reverse genetics system to generate a pool of >200 isogenic SARS-CoV-2 viruses harboring specific 6-nucleotide barcodes inserted in ORF10, a non-translated ORF. We directly inoculated donor Syrian hamsters intranasally with this barcoded virus pool and exposed a paired naive contact hamster to each donor. Following exposure, the nasal turbinates, trachea, and lungs were collected, viral titers were measured, and the number of barcodes in each tissue were enumerated to quantify the transmission bottleneck. The duration and route (airborne, direct contact, and fomite) of exposure were varied to assess their impact on the transmission bottleneck. In airborne-exposed hamsters, the transmission bottleneck increased with longer exposure durations. We found that direct contact exposure produced the largest transmission bottleneck (average 27 BCs), followed by airborne exposure (average 16 BCs) then fomite exposure (average 8 BCs). Interestingly, we detected unique BCs in both the upper and lower respiratory tract of contact animals from all routes of exposure, suggesting that SARS-CoV-2 can directly infect hamster lungs. Altogether, these findings highlight the utility of barcoded viruses as tools to rigorously study virus transmission. In the future, barcoded SARS-CoV-2 will strengthen studies of immune factors that influence virus transmission.

microbiology↗

bioRxiv2023

Genome editing induces the transfer of mitochondrial DNA into the nuclear genome

Mitochondria serve as the cellular powerhouse, and their distinct DNA makes them a prospective target for gene editing to treat genetic disorders. However, the impact of genome editing on mitochondrial DNA (mtDNA) stability remains a mystery. Our study reveals previously unknown risks of genome editing that both nuclear and mitochondrial editing cause broad transfer of mitochondrial DNA segments into the nuclear genome in various cell types including human cell lines, primary T cells, retinal cells, and mouse embryos. Furthermore, drug-induced mitochondrial stresses and mtDNA breaks exacerbate this transfer of mtDNA into the nuclear genome. Notably, we observe that the newly developed mitochondrial base editor DdCBE can also cause widespread mtDNA integrations. However, we provide a practical solution to suppress the transfer of mtDNA by co-expressing TREX1 or TREX2 exonucleases during DdCBE editing. These findings also shed light on the origins of mitochondrial-nuclear DNA segments.

genomics↗

bioRxiv2023

The highly conserved stem-loop II motif is dispensable for SARS-CoV-2

The stem-loop II motif (s2m) is a RNA structural element that is found in the 3 untranslated region (UTR) of many RNA viruses including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Though the motif was discovered over twenty-five years ago, its functional significance is unknown. In order to understand the importance of s2m, we created viruses with deletions or mutations of the s2m by reverse genetics and also evaluated a clinical isolate harboring a unique s2m deletion. Deletion or mutation of the s2m had no effect on growth in vitro, or growth and viral fitness in Syrian hamsters in vivo. We also compared the secondary structure of the 3 UTR of wild type and s2m deletion viruses using SHAPE-MaP and DMS-MaPseq. These experiments demonstrate that the s2m forms an independent structure and that its deletion does not alter the overall remaining 3UTR RNA structure. Together, these findings suggest that s2m is dispensable for SARS-CoV-2. IMPORTANCERNA viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contain functional structures to support virus replication, translation and evasion of the host antiviral immune response. The 3 untranslated region of early isolates of SARS-CoV-2 contained a stem-loop II motif (s2m), which is a RNA structural element that is found in many RNA viruses. This motif was discovered over twenty-five years ago, but its functional significance is unknown. We created SARS-CoV-2 with deletions or mutations of the s2m and determined the effect of these changes on viral growth in tissue culture and in rodent models of infection. Deletion or mutation of the s2m element had no effect on growth in vitro, or growth and viral fitness in Syrian hamsters in vivo. We also observed no impact of the deletion on other known RNA structures in the same region of the genome. These experiments demonstrate that the s2m is dispensable for SARS-CoV-2.

microbiology↗

bioRxiv2021

Cohesin modulates DNA replication to preserve genome integrity

Cohesin participates in loop formation by extruding DNA fibers from its ring-shaped structure. Cohesin dysfunction eliminates chromatin loops but only causes modest transcription perturbation, which cannot fully explain the frequently observed mutations of cohesin in various cancers. Here, we found that DNA replication initiates at more than one thousand extra dormant origins after acute depletion of RAD21, a core subunit of cohesin, resulting in earlier replicating timing at approximately 30% of the human genomic regions. In contrast, CTCF is dispensable for suppressing the early firing of dormant origins that are distributed away from the loop boundaries. Furthermore, greatly elevated levels of gross DNA breaks and genome-wide chromosomal translocations arise in RAD21-depleted cells, accompanied by dysregulated replication timing at dozens of hotspot genes. Thus, we conclude that cohesin coordinates DNA replication initiation to ensure proper replication timing and safeguards genome integrity.

genetics↗

bioRxiv2020

Osteoprotegerin is elevated in pulmonary fibrosis and associates with IPF progression

Osteoprotegerin (OPG), a decoy receptor for receptor activator of NF-kB ligand (RANKL), is used as a biomarker for assessing severity of liver fibrosis. However, its expression and role in pulmonary fibrosis are unknown. We hypothesized that OPG also has a role in pulmonary fibrosis. Human and mouse control and fibrotic lung tissue were used to examine OPG expression, and mouse precision-cut lung slices to study OPG regulation in pulmonary fibrosis. Serum from idiopathic pulmonary fibrosis (IPF) patients and controls was analysed to investigate whether OPG levels correlate with disease status as measured by lung function. OPG-protein levels were significantly higher in mouse and human fibrotic lung tissue compared to control. OPG-mRNA and protein production were induced in mouse precision-cut-lung slices upon TGF{beta} stimulation and could be inhibited with galunisertib, a TGF{beta} receptor kinase inhibitor. OPG-protein levels in fibrotic mouse lung tissue correlated with degree of fibrosis. Isolated lung fibroblasts from IPF patients had higher OPG-protein levels than control fibroblasts. Serum OPG levels in IPF patients, at first presentation, negatively correlated with diffusing capacity to carbon monoxide. Finally, serum OPG levels higher than 1234 pg/ml at first presentation were associated with progression of disease in IPF patients. In conclusion, OPG is produced in lung tissue, associates with fibrosis, and may be a potential prognostic biomarker for IPF disease progression. Validation in a larger cohort is warranted to further explore the role of OPG in pulmonary fibrosis and its potential for assessing the prognosis of fibrotic lung disease in individual patients. Take home messageOsteoprotegerin is present in fibrotic lung tissue and high serum levels correlate with low lung function and IPF disease progression in this small study, indicating osteoprotegerin may have value as a biomarker to predict IPF progression

pathology↗

bioRxiv2018

Microbial Cells Harboring a Mitochondrial Gene Are Capable of CO2 Capture

Global warming is escalating with increased temperatures reported worldwide. Given the enormous land mass on the planet, biological capture of CO2 remains a viable approach to mitigate the crisis as it is economical and easy to implement. In this study, a gene capable of CO2 capture was identified via selection in minimal media. This mitochondrial gene named as OG1 encodes the OK/SW-CL.16 protein and shares homology with cytochrome oxidase subunit III of various species and PII uridylyl-transferase from Loktanella vestfoldensis SKA53. CO2 capture experiments indicate that {delta}13C was substantially higher in the cells harboring the gene OG1 than the control in the nutrition-poor media. This study suggests that CO2 capture using engineered microorganisms in barren land can be exploited to address the soaring CO2 level in the atmosphere, opening up vast land resources to cope with global warming.\n\nIMPORTANCEGlobal warming crisis is deteriorating with increased CO2 levels in the atmosphere each year. Action must be taken before catastrophic consequences occur in the not-so-distant future. Biological capture of CO2 is a feasible approach to alleviate the current crisis. We have identified a mitochondrial gene which demonstrated CO2 utilization capability. Data presented in this study suggest that CO2 capture using engineered microorganisms can be harnessed to address the ever-rising CO2 level in the atmosphere.

bioengineering↗