Biology subjects

li, J.

Publications and source records attributed to li, J..

4 recordsLinked to original sources

bioRxiv2023

Cryo-EM structure of DNA polymerase θ helicase domain in complex with inhibitor novobiocin

DNA double-strand breaks (DSBs) are highly toxic lesions that occur during the cellular metabolic process. DNA Polymerase theta (Pol{theta}) is an error-prone polymerase that has been implicated in the repair of chromosome breaks, recovery of broken replication forks, and translesion synthesis. The inhibition of Pol{theta} activity has been implicated in killing HR-deficient tumor cells in vitro and in vivo. We present the first biochemical evidence that the antibiotics novobiocin (NVB) noncompetitively inhibit ATP hydrolysis by the ATPase domain of the Pol{theta} helicase domain (Pol{theta}-HLD). We report the Cryo-EM structure of apo dimeric Pol{theta} helicase domain (Pol{theta}-HLD), and the first inhibitor occupied Pol{theta}-HLD structure. Our structure identifies a non-canonical novobiocin binding pocket, distinct from the canonical site that partially overlaps with the ATP in the ATPase domain. Comparison with the homolog helicase Hel308-DNA duplex complex suggests that the novobiocin competitively binds to a triangle hub on the DNA translocation pathway and blocks the ssDNA binding and translocation. Furthermore, the first dimeric structure of Pol{theta}-HLD also provides a structural framework for revealing the microhomology-mediated end-joining mechanism. Our results demonstrate that the inhibitor-occupied structure combined with rational, structure-based drug design will undoubtedly accelerate the discovery of potent inhibitors with better efficacy and target selectivity to human Pol{theta}.

biochemistry↗

bioRxiv2022

Social Regulation of Egg Size Plasticity in the Honey Bee is Mediated by Cytoskeleton Organizer Rho1

Egg size plasticity represents an adaptive reproductive strategy in numerous organisms, including the honey bee, Apis mellifera. However, the proximate causation of this plasticity and egg size in general is unknown. We show that honey bee queens predictably and reversibly adjust egg size in response to their colony size and that this plasticity is an active response to the queens perception of colony size instead of a consequence of egg laying rate. The egg size increase involves changes of 290 ovarian proteins, mostly related to increased energy metabolism, protein transport, and cytoskeleton functions. Spatio-temporal expression analysis of the small GTPase Rho1 indicates its central role in egg size regulation, which we confirm by RNAi-mediated gene knock-down and expression analyses. The molecular adjustments that promote maternal investment of honey bee queens in response to their social environment thus reveal a novel mechanism of egg size regulation.

evolutionary biology↗

bioRxiv2022

Improved Heat Tolerance in Heat-acclimated Mice: the Probable Role of the PD-L1 Pathway

Heat stroke is a life-threatening illness and is related to systematic inflammation-induced multiple organ dysfunction. Available evidence indicates that the severity of the systematic inflammatory response in heat stroke may be related to the changes in immune regulation brought by heat acclimation. However, the mechanisms of heat acclimation are still unclear. Here, we assessed the differences in immunocyte subsets in the spleen and lymph nodes of heat-acclimated and unacclimated mice. A higher frequency of CD4+Foxp3+ Tregs was observed in heat-acclimated mice. Our results indicated that the improved heat tolerance exhibited during acute heat stress exposure was related to an increased number of Tregs. In heat-acclimated mice, an increase in the number of Tregs was able to mitigate the recruitment of neutrophils, inhibit the activation of neutrophils, and suppress the severity of acute inflammation. Increased differentiation and development of Tregs in peripheral immune organs in heat-acclimated mice might stem from enhanced expression of Foxp3 and PD-L1. Our results strongly suggest that the regulatory function of increased Tregs on neutrophils may be regulated through the PD-1/PD-L1 pathway. The anti-inflammatory effects of Tregs have never been studied in the context of heat stress-induced systemic inflammation. Thus, our results on immunoregulation involving Tregs in heat-acclimated mice might be significant for devising a potential treatment for systemic inflammatory response syndrome and heatstroke.

immunology↗

bioRxiv2022

Effective infection with dengue virus in experimental neonate and adult mice through intranasal route

As a member of the family Flaviviridae, the dengue virus is transmitted to humans through mosquito vectors. The virus causes dengue fever with flu-like symptoms, life-threatening dengue hemorrhagic fever, and dengue shock syndrome that affects four billion people in 128 countries. It can also be transmitted through atypical routes, such as needle stick injury, vertical transmission, and the receipt of contaminated blood or organs. Although sporadic cases cannot be classified as atypical transmission routes and raise respiratory exposure concerns, the risks remain unclear. Here, we analyzed the respiratory infectivity of the dengue virus in BALB/c suckling and A6 adult mice using the dengue virus serotype 2 and intranasal inoculation. The results showed that the clinical symptoms of intranasally infected mice included excitement, emaciation, malaise, and death, and histopathological changes and viremia dynamics were observed in multiple tissues, including the brain, liver, and spleen. Notably, the DENV serotype 2 showed clear brain tropism after intranasal infection, and viral loads peaked at seven days post-inoculation. Furthermore, the virus was isolated from mouse brains, and the sequence homology between the viral stock and dengue virus isolates was 99.99%. Similar results were observed in adult IFN-/{beta} receptor-deficient mice. Taken together, our results suggest that the DENV serotype 2 can infect suckling mice and adult immune-deficient mice via the nasal route. The results of our study broaden our perception of atypical dengue transmission routes and may help explain dengue virus infections that occur without the presence of mosquito vectors. ImportanceDengue is transmitted mainly via mosquito vectors. Flu-like dengue fever or life-threatening severe dengue threatens four billion people in 128 countries. Non-vector dengue cases have occurred occasionally since 1990. These cases cannot be classified as atypical transmission routes and are suspected to have arisen via sexual or respiratory transmission. Recently, the sexual transmission of dengue has been confirmed in humans. The respiratory infectivity of other members of the Flaviviridae family, such as Zika and Japanese encephalitis viruses, has been determined under experimental conditions. The potential for respiratory infection with the dengue virus has not yet been confirmed. In this study, we analyzed the respiratory infectivity of the dengue virus in suckling mice and adult immunodeficient mice via intranasal inoculation, thereby exploring the potential for respiratory transmission in cases with non-vector dengue infection, especially for patients who were exposed to dengue virus contaminants.

microbiology↗