Biology subjects

Powell, T. J.

Publications and source records attributed to Powell, T. J..

4 recordsLinked to original sources

bioRxiv2026

Transcription directs Holliday junction branch migration

During meiosis, genetic diversity arises from the resolution of branched DNA intermediates called Holliday junctions to create crossovers--sites of reciprocal exchange between parental chromosomes. Holliday junctions arise during the repair of Spo11-induced DNA breaks, yet the principles linking break formation, repair, and chromosome architecture remain unclear. Top3, a type IA topoisomerase, acts on Holliday junctions, but its spatiotemporal dynamics are unknown. Here, we map Top3 catalytic activity throughout meiotic prophase with strand specificity and nucleotide resolution. We identify a DNA sequence motif associated with catalysis and a pattern of activity around Spo11 hotspots that requires ongoing repair and Top3s helicase partner, Sgs1. Strikingly, Top3 activity shifts over time, influenced by transcription, cohesin, and the crossover factors Msh5 and Mer3, redistributing toward sites of convergent transcription--known locations of meiotic cohesin association. Upon prophase exit, as crossovers are resolved, Top3 activity subsides. Remarkably, maps of genome-wide recombination reveal that crossover resolution preferentially occurs at these same regions of convergent transcription. Collectively, we propose that Top3 coordinates the transcription-coupled movement of Holliday junctions from Spo11 hotspots towards cohesin-associated axis sites, whereupon crossover resolution occurs to ensure accurate meiotic chromosome segregation.

molecular biology↗

bioRxiv2020

Epithelial Cell Regulation of Type 2 Cytokine Release by Peripheral Blood Mononuclear Cells

BackgroundType 2 cytokines such as IL-13 and IL-5 are important drivers of pathophysiology and exacerbation in asthma. Defining how these type 2 cytokine responses are regulated is a research priority. Epithelial cells promote type 2 responses by releasing alarmins including IL-25, IL-33 and TSLP, but much less is known about inhibitory factors. MethodsIL-13 release was measured from peripheral blood mononuclear cells (PBMC) cultured with Interleukin (IL)-2 for five days. Epithelial cell lines or human bronchial epithelial cells (HBEC) isolated from healthy or asthma donors were added to these PBMC cultured with IL-2 and release of IL-13 or IL-5 measured. To characterise the mechanisms, we assessed the effect of mechanical disruption of epithelial cells, addition of the COX inhibitor indomethacin and the G-protein inhibitor pertussis toxin. ResultsPBMC cultured with IL-2 secreted type 2 cytokines in a cell number and time dependent manner. Epithelial cell lines inhibited IL-13 and IL-5 release after co-culture with PBMC in the presence of IL-2, directly, across a transwell and using epithelial cell supernatant. Cells or supernatant from HBEC from healthy or asthma donors also inhibited the cytokine release. Trypsin treatment of conditioned media indicated that inhibitory factor(s) are trypsin insensitive. Mechanical disruption of epithelial cells or indomethacin treatment had no effect, but pertussis toxin reduced epithelial cell inhibition of IL-2 driven type 2 cytokine release. ConclusionEpithelial cells regulate cytokine release by soluble factor(s) and this could be an important immunoregulatory function of the airway epithelium.

immunology↗

bioRxiv2020

Identification of lactate as a potential inhibitory factor within epithelial cell supernatant and its effects on type 2 T cell populations

Abstract / Short SummaryEpithelial cells have been shown previously to inhibit release of type 2 cytokines from T cells and this process could be important in a type 2-mediated diseases such as asthma. Factors secreted by epithelial cells could regulate inflammatory responses and release an all is well signal such that the immune system is controlled. Here we show that lung epithelial cells are able to inhibit IL-2 driven type 2 cytokine release by PBMC cells across a transwell indicating the involvement of soluble mediators. We then fractionate the mediators within the conditioned media using methanol chloroform separation and size fractionation. Inhibitory activity was demonstrated within the polar fraction of supernatant separated by methanol chloroform extraction. We then found that lactate, a component within the polar fraction was able to mediate inhibition of the type 2 cytokines. The inhibitory activity of lactate deserves further study and could play a role in the inhibition of T cell derived cytokines in vivo.

immunology↗

bioRxiv2017

A single cycle influenza virus coated in H7 hemagglutinin provides heterotypic protection and neutralising antibody responses to both glycoproteins.

A non-replicating form of pseudotyped influenza virus, inactivated by suppression of the hemagglutinin signal sequence (S-FLU), can act as a broadly protective vaccine. S-FLU can infect for a single round only, and induces heterotypic protection predominantly through activation of cross-reactive T cells in the lung. Unlike the licensed live attenuated virus, it cannot reassort a pandemic HA into seasonal influenza. Here we present data on four new forms of S-FLU coated with the H7 hemagglutinins from A/Anhui/1/2013 and A/Shanghai/1/2013, H7N9 viruses that emerged recently in China, and A/Netherlands/219/2003 and A/New York/107/2003. We show that vaccination in the lung induced a strong local CD8 T cell response and protected against heterosubtypic X31 (H3N2) virus and highly virulent PR8 (H1N1), but not influenza B virus. Lung vaccination also induced a strong neutralising antibody response to the encoded neuraminidase. If given at higher dose in the periphery, H7 S-FLU induced a specific neutralising antibody response to H7 hemagglutinin coating the particle. Polyvalent vaccination with mixed H7 S-FLU induced a broadly neutralising antibody response to all four H7 strains. S-FLU is a versatile vaccine candidate that could be rapidly mobilized ahead of a new pandemic threat.

immunology↗