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Zhongwei Zhao

Publications and source records attributed to Zhongwei Zhao.

8 recordsLinked to original sources
PubMed2026

Activation of mTOR pathway by human cytomegalovirus promoting host ribosomal protein expression by coordinated transcriptional and translational controls.

Human cytomegalovirus (HCMV) profoundly reprograms host transcription and RNA metabolism, yet its impact on transcription start site (TSS) regulation of host genes remains poorly understood. Here, we employed NanoCap Analysis of Gene Expression sequencing (NanoCAGE-seq) to investigate HCMV-driven changes in alternative TSS usage across the host transcriptome. We identified widespread TSS switching, with ribosomal protein genes (RPGs) emerging as a highly enriched category. Alternative TSS usage produced isoforms with distinct 5'untranslated regions (UTRs), thereby altering cis-regulatory elements that shape translational efficiency. Integrative transcriptomic and proteomic analyses revealed a paradoxical accumulation of RPG proteins despite transcriptional downregulation during infection. Using 5' Rapid Amplification of cDNA Ends (5'RACE), we characterized four RPGs of RPL4, RPS11, RPS23, and RPS24 that generated 5'UTR variants through alternative TSS usage. Notably, isoforms containing a 5'terminal oligopyrimidine (5'TOP) motif were significantly enriched, correlating with mTOR activation induced by HCMV. Functional assays with bicistronic reporter constructs in HEK293 cells and infection models in human embryonic lung fibroblasts demonstrated that the RPL4 5'TOP isoform exhibited enhanced mTORC1-driven translation compared with non-5'TOP counterparts. Importantly, RPL4 upregulation facilitated viral protein synthesis and boosted production of infectious virions. Together, our findings reveal that dynamic TSS switching of RPGs provides a simple, yet effective, mechanism for fine-tuning mTORC1-responsive translation. By co-opting host transcriptional and translational programs, HCMV enhances ribosome function to optimize the cellular environment for productive viral replication.

Humans↗
PubMed2006

The iron-sulfur clusters in Escherichia coli succinate dehydrogenase direct electron flow.

Succinate dehydrogenase is an indispensable enzyme involved in the Krebs cycle as well as energy coupling in the mitochondria and certain prokaryotes. During catalysis, succinate oxidation is coupled to ubiquinone reduction by an electron transfer relay comprising a flavin adenine dinucleotide cofactor, three iron-sulfur clusters, and possibly a heme b556. At the heart of the electron transport chain is a [4Fe-4S] cluster with a low midpoint potential that acts as an energy barrier against electron transfer. Hydrophobic residues around the [4Fe-4S] cluster were mutated to determine their effects on the midpoint potential of the cluster as well as electron transfer rates. SdhB-I150E and SdhB-I150H mutants lowered the midpoint potential of this cluster; surprisingly, the His variant had a lower midpoint potential than the Glu mutant. Mutation of SdhB-Leu-220 to Ser did not alter the redox behavior of the cluster but instead lowered the midpoint potential of the [3Fe-4S] cluster. To correlate the midpoint potential changes in these mutants to enzyme function, we monitored aerobic growth in succinate minimal medium, anaerobic growth in glycerol-fumarate minimal medium, non-physiological and physiological enzyme activities, and heme reduction. It was discovered that a decrease in midpoint potential of either the [4Fe-4S] cluster or the [3Fe-4S] cluster is accompanied by a decrease in the rate of enzyme turnover. We hypothesize that this occurs because the midpoint potentials of the [Fe-S] clusters in the native enzyme are poised such that direction of electron transfer from succinate to ubiquinone is favored.

Electron Spin Resonance Spectroscopy↗
PubMed2006

Trichinella spiralis: histamine secretion induced by TSL-1 antigens from unsensitized mast cells.

Mast cells' hyperplasia and activation are prominent features in Trichinella spiralis infection. Recently, it was shown that TSL-1 antigens from T. spiralis muscle larvae induce IL-4 and TNF release by unsensitized, normal mast cells (MC) involving an Ig-independent mechanism. In this study, we characterized histamine secretion induced by TSL-1 antigens from normal, unsensitized rat peritoneal MC. Maximum histamine secretion (30+/-5.3% SEM, n=13) was achieved with 30 ng/mL TSL-1 antigens. However, TSL-1 did not induce an increase in beta-hexosaminidase release or NADPH oxidase activity by MC. Interestingly, histamine secretion by TSL-1 was completed at 10s, and was inhibited by both Bordetella pertussis toxin and neuraminidase V, characteristics similar to those involved in substance P-induced histamine secretion. However, in contrast to substance P, TSL-1 induced histamine secretion in the absence of detectable changes in intracellular Ca(2+). We are investigating the molecular pathways involved in MC activation by TSL-1.

Animals↗
PubMed2006

Effects of site-directed mutations in Escherichia coli succinate dehydrogenase on the enzyme activity and production of superoxide radicals.

Escherichia coli succinate dehydrogenase (SdhCDAB) catalyzes the oxidation of succinate to fumarate in the Krebs cycle, and during turnover, it produces superoxide radicals. SdhCDAB is a good model system for the succinate dehydrogenase (Sdh) found in the mitochondrial respiratory chain (complex II), as the subunits are structural homologues. Although mutations in sdh genes are reportedly associated with a variety of mitochondria-related diseases, the molecular mechanism of these diseases is poorly understood. We have investigated the effects of site-directed mutations around the heme (SdhD-H71L and SdhC-H91L), and at the ubiquinone-binding site (Q site; SdhC-I28E), on enzyme activity and production of superoxide radicals. The mutations SdhD-H71L and SdhC-I28E, but not SdhC-H91L, significantly reduce the succinate-ubiquinone reductase activity of the enzyme. All 3 mutant enzymes produce more superoxide than the wild-type enzyme, indicating that disturbance of the heme or the Q site can enhance superoxide production. The presence of a Q-site inhibitor reduces superoxide production significantly. Furthermore, the yield of superoxide is substrate dependent and increases with succinate concentration from 0.1 to 10 mmol/L. Our results indicate that, in SdhCDAB, the Q site with bound ubiquinone is an important source of superoxide radicals.

Binding Sites↗
PubMed2003

Effects of site-directed mutations on heme reduction in Escherichia coli nitrate reductase A by menaquinol: a stopped-flow study.

We have studied the effects of site-directed mutations in Escherichia coli nitrate reductase A (NarGHI) on heme reduction by a menaquinol analogue (menadiol) using the stopped-flow method. For NarGHI(H66Y) and NarGHI(H187Y), both lacking heme b(L) but having heme b(H), the heme reduction by menadiol is abolished. For NarGHI(H56R) and NarGHI(H205Y), both without heme b(H) but with heme b(L), a smaller and slower heme reduction compared to that of the wild-type enzyme is observed. These results indicate that electrons from menadiol oxidation are transferred initially to heme b(L). A transient species, likely to be associated with a semiquinone radical anion, was generated not only on reduction of the wild-type enzyme as observed previously (1) but also on reduction of NarGHI(H56R) and NarGHI(H205Y). The inhibitors 2-n-heptyl-4-hydroxyquinoline-N-oxide and stigmatellin both have significant effects on the reduction kinetics of NarGHI(H56R) and NarGHI(H205Y). We have also investigated the reoxidation of menadiol-reduced heme by nitrate in the mutants. Compared to the wild type, no significant heme reoxidation is observed for NarGHI(H56R) and NarGHI(H205Y). This result indicates that a single mutation removing heme b(H) blocks the electron-transfer pathway from the subunit NarI to the catalytic dimer NarGH.

Arginine↗
PubMed2003

Transient kinetic studies of heme reduction in Escherichia coli nitrate reductase A (NarGHI) by menaquinol.

We have studied the transient kinetics of quinol-dependent heme reduction in Escherichia coli nitrate reductase A (NarGHI) by the menaquinol analogue menadiol using the stopped-flow method. Four kinetic phases are observed in the reduction of the hemes. A transient species, likely to be associated with a semiquinone radical anion, is observed with kinetics that correlates with one of the phases. The decay of the transient species and the formation of the second reduction phase of the hemes can be fitted to a double-exponential equation giving similar rate constants, k(1) = 9.24 +/- 0.9 s(-1) and k(2) = 0.22 +/- 0.02 s(-1) for the decay of the transient species, and k(1) = 9.23 +/- 0.9 s(-1) and k(2) = 0.22 +/- 0.02 s(-1) for the formation of the reduction phase. The quinol-binding-site inhibitors 2-n-heptyl-4-hydroxyquinoline-N-oxide (HOQNO) and stigmatellin have significant and different inhibitory effects on the reduction kinetics. The kinetics of heme reduction in NarI expressed in the absence of the NarGH catalytic dimer (NarI(DeltaGH) exhibits only two kinetic phases, and the decay of the transient species also correlates kinetically with the second reduction phase of the hemes. We have also studied nitrate-dependent heme reoxidation following quinol-dependent heme reduction using a sequential stopped-flow method. HOQNO elicits a much stronger inhibitory effect than stigmatellin on the reoxidation of the hemes. On the basis of our results, we propose schemes for the mechanism of NarGHI reduction by menaquinol and reoxidation by nitrate.

Catalysis↗
PubMed2003

On the Far Eastern pattern of mortality.

Since the early 1980s, it has been accepted widely that there is a Far Eastern pattern of mortality, a pattern characterized by excessively high death rates among older men relative to death rates among younger men and among women. It has been regarded as a unique regional mortality pattern, applying primarily to Far Eastern populations. A re-examination of the mortality data of some Far Eastern populations reveals that changes in both age patterns of and sex differentials in mortality have been widely observed. Further, mortality patterns similar to the so-called Far Eastern mortality model have been found in many other populations.

Asia, Eastern↗