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Biology subjects

Zhai, Y.

Publications and source records attributed to Zhai, Y..

61 records · Page 4Linked to original sources

A Novel Neoantigen Discovery Approach based on Chromatin High Order Conformation: Mapping the Neoantigen to 3D Genome

The high-throughput sequencing technology has yielded reliable and ultra-fast sequencing for DNA and RNA. For tumor cells of cancer patients, when combining the results of DNA and RNA sequencing, one can identify potential neoantigens that stimulate immune response of the T cells. However, when the somatic mutations are abundant, it is computationally challenging to efficiently prioritize the identified neoantigen candidates according to their ability of activating the T cell immuno-response. Numerous prioritization or prediction approaches have been proposed to address this issue but none of them considers the original DNA loci of the neoantigens from the perspective of 3D genome. Here we retrospect the DNA origins of the immune-positive and non-negative neoantigens in the context of 3D genome and discovered that 1) DNA loci of the immuno-positive neoantigens tend to cluster genome-wise. 2) DNA loci of the immuno-positive neoantigens tend to belong to active chromosomal compartment (compartment A) in some chromosomes. 3). DNA loci of the immuno-positive neoantigens tend to locate at specific regions in the 3D genome. We believe that the 3D genome information will help more precise neoantigen prioritization and discovery and eventually benefit precision and personalized medicine in cancer immunotherapy.

bioinformatics↗

Cryo-EM structures reveal a conformational change of SOPA1 during mitochondrial inner membrane fusion

Mammalian mitochondrial inner membrane fusion is mediated by OPA1(optic atrophy 1). Under physiological condition, OPA1 undergoes proteolytic processing to form a membrane-anchored long isoform (LOPA1) and a soluble short isoform (SOPA1). A combination of LOPA1 and SOPA1 are required for membrane fusion, however, the relevant mechanism is not well understood. In this study, we investigate the cryo-EM structures of SOPA1 coated liposome tube at nucleotide-free and GTP{gamma}S bound states. SOPA1 exhibits a general structure of dynamin family and can assemble onto membrane in a helical array with a building block of dimer and thus induce membrane tubulation. A predicted amphipathic helix is discovered to mediate the tubulation activity of SOPA1. The binding of GTP{gamma}S causes a conformational rotation between GTPase domain and stalk region, and then induces a rearrangement of the helical array and an expansion of the tube, which is opposite to the behavior of other dynamin proteins, suggesting a unique role of SOPA1 in the fusion of mitochondrial inner membrane.

biophysics↗

Gamblers: an Antibiotic-induced Evolvable Cell Subpopulation Differentiated by Reactive-oxygen-induced General Stress Response

Antibiotics can induce mutations that cause antibiotic resistance. Yet, despite their importance, mechanisms of antibiotic-promoted mutagenesis remain elusive. We report that the fluoroquinolone antibiotic ciprofloxacin (cipro) induces mutations that cause drug resistance by triggering differentiation of a mutant-generating cell subpopulation, using reactive oxygen species (ROS) to signal the sigma-S ({sigma}S) general-stress response. Cipro-generated DNA breaks activate the SOS DNA-damage response and error-prone DNA polymerases in all cells. However, mutagenesis is restricted to a cell subpopulation in which electron transfer and SOS induce ROS, which activate the {sigma}S response, allowing mutagenesis during DNA-break repair. When sorted, this small {sigma}S-response-\"on\" subpopulation produces most antibiotic cross-resistant mutants. An FDA-approved drug prevents {sigma}S induction specifically inhibiting antibiotic-promoted mutagenesis. Furthermore, SOS-inhibited cell division, causing multi-chromosome cells, is required for mutagenesis. The data support a model in which within-cell chromosome cooperation together with development of a \"gambler\" cell subpopulation promote resistance evolution without risking most cells.

microbiology↗

Bacteria-to-human protein networks reveal origins of endogenous DNA damage

DNA damage provokes mutations and cancer, and results from external carcinogens or endogenous cellular processes. Yet, the intrinsic instigators of DNA damage are poorly understood. Here we identify proteins that promote endogenous DNA damage when overproduced: the DNA-damaging proteins (DDPs). We discover a large network of DDPs in Escherichia coli and deconvolute them into six DNA-damage-causing function clusters, demonstrating DDP mechanisms in three: reactive-oxygen increase by transmembrane transporters, chromosome loss by replisome binding, and replication stalling by transcription factors. Their 284 human homologs are over-represented among known cancer drivers, and their expression in tumors predicts heavy mutagenesis and poor prognosis. Half of tested human homologs, when overproduced in human cells, promote DNA damage and mutation, with DNA-damaging mechanisms like those in E. coli. Together, our work reveals DDP networks that provoke endogenous DNA damage and may indicate functions of many human known and newly implicated cancer-promoting proteins.

cancer biology↗

New interfaces on MiD51 for Drp1 recruitment and regulation

Mitochondrial fission is facilitated by dynamin-related protein Drp1 and a variety of its receptors. However, the molecular mechanism of how Drp1 is recruited to the mitochondrial surface by receptors MiD49 and MiD51 remains elusive. Here, we showed that the interaction between Drp1 and MiD51 is regulated by GTP binding and depends on the polymerization of Drp1. We identified two regions on MiD51 that directly bind to Drp1, and found that dimerization of MiD51 via an intermolecular disulfide bond between C452 residues is required for MiD51 to directly interact with Drp1. Our Results have suggested a multi-faceted regulatory mechanism for the interaction between Drp1 and MiD51 that illustrates the potentially complicated and tight regulation of mitochondrial fission.

biophysics↗

Large protein complex production using the SmartBac System - Strategies and Applications

Recent revolution of cryo-electron microscopy has opened a new door to solve high-resolution structures of macromolecule complexes without crystallization while how to efficiently obtain homogenous macromolecule complex sample is therefore becoming a bottleneck. Here we report SmartBac, an easy and versatile system for constructing large-sized transfer plasmids used to generate recombinant baculoviruses that express large multiprotein complexes in insect cells. The SmartBac system integrates the univector plasmid-fusion system, Gibson assembly method and polyprotein strategy to construct the final transfer plasmids. The fluorescent proteins are designed to be co-expressed with recombinant proteins to monitor transfection and expression efficiencies. A scheme of screening an optimal tagged subunit for effective purification is provided. Six large multiprotein complexes including the human exocyst complex and dynactin complex were successfully expressed, suggesting a great potential of SmartBac for its wide application in the future structural biology study.

bioengineering↗

Inhibition of mitochondrial fission preserves photoreceptors after retinal detachment

Photoreceptor degeneration is a leading cause of visual impairment worldwide. Separation of neurosensory retina from the underlying retinal pigment epithelium is a prominent feature preceding photoreceptor degeneration in a variety of retinal diseases. Although ophthalmic surgeries have been well developed to restore retinal structures, post-op patients usually experience progressive photoreceptor degeneration and irreversible vision loss that is incurable at present. Previous studies point to a critical role of mitochondria-mediated apoptotic pathway in photoreceptor degeneration, but the upstream triggers remain largely unexplored. In this study, we show that after experimental RD induction, photoreceptors activate dynamin-related protein 1 (Drp1)-dependent mitochondrial fission pathway and subsequent apoptotic cascades. Mechanistically, endogenous ROS is necessary for Drp1 activation in vivo and exogenous ROS insult is sufficient to activate Drp1-dependent mitochondrial fission in cultured photoreceptors. Accordingly, inhibition of Drp1 activity effectively preserves mitochondrial integrity and rescues photoreceptors. Collectively, our data delineates a ROS-Drp1-mitochondria axis that promotes photoreceptor degeneration in retinal diseased models.

neuroscience↗