Biology subjects

Hegedus, Z.

Publications and source records attributed to Hegedus, Z..

3 recordsLinked to original sources

bioRxiv2021

Understanding p300-transcription factor interactions using sequence variation and hybridization

The hypoxic response is central to cell function and plays a significant role in the growth and survival of solid tumours. HIF-1 regulates the hypoxic response by activating over 100 genes responsible for adaptation to hypoxia, making it a potential target for anticancer drug discovery. Although there is significant structural and mechanistic understanding of the interaction between HIF-1 and p300 alongside negative regulators of HIF-1 such as CITED2, there remains a need to further understand the sequence determinants of binding. In this work we use a combination of protein expression, chemical synthesis, fluorescence anisotropy and isothermal titration calorimetry for HIF-1 sequence variants and a HIF-1- CITED hybrid sequence which we term CITIF. We show the HIF-1 sequence is highly tolerant to sequence variation through reduced enthalpic and less unfavourable entropic contributions, These data imply backbone as opposed to side chain interactions and ligand folding control the binding interaction and that sequence variations are tolerated as a result of adopting a more disordered bound interaction or "fuzzy" complex.

biochemistry↗

bioRxiv2021

Nicotinate degradation in a microbial eukaryote: a novel, complete pathway extant in Aspergillus nidulans

Several strikingly different aerobic and anaerobic pathways of nicotinate utilization had been described in bacteria. No similar work is extant in any eukaryote. Here we elucidate a complete eukaryotic nicotinate utilization pathway, by constructing single or multiple gene deleted strains and identifying metabolic intermediates by ultra-high performance liquid chromatography - high-resolution mass spectrometry. Enzymes catalyzing each step and all intermediate metabolites were identified. We previously established that the cognate eleven genes organized in three clusters constitute a regulon, strictly dependent on HxnR, a pathway-specific transcription factor. The first step, hydroxylation of nicotinic acid to 6-hydroxynicotinic acid is analogous to that occurring in bacterial pathways and is catalyzed by an independently evolved molybdenum-containing hydroxylase. The following enzymatic steps have no prokaryotic equivalents: 6-hydroxynicotinic acid is converted to 2,3,6-trihydroxypyridine through 2,5-dihydroxypiridine and the trihydroxylated pyridine ring is then saturated to 5,6-dihydroxypiperidine-2-one followed by the oxidation of the C6 hydroxyl group resulting in 3-hydroxypiperidine-2,6-dione. The latter two heterocyclic compounds are newly identified cellular metabolites, while 5,6-dihydroxypiperidine-2-one is a completely new chemical compound. Ring opening between C and N results in -hydroxyglutaramate, an unprecedented compound in prokaryotic nicotinate catabolic routes. The pathway extant in A. nidulans, and in many other ascomycetes, is different from any other previously analyzed in bacteria. Our earlier phylogenetic analysis of Hxn proteins together with the complete novel biochemical pathway we now describe further illustrates the convergent evolution of catabolic pathways between fungi and bacteria. Significance StatementThis eukaryotic nicotinate catabolic pathway illustrates the convergent evolution of prokaryotic and microbial eukaryotic metabolism. It brings to light newly identified metabolites and step processing enzymes. The identification of hitherto undescribed metabolites - which could serve as precursor biosynthetic molecules - is potentially relevant to both pharmaceutical and agrochemical industries.

microbiology↗

bioRxiv2019

Myeloid Tribbles 1 induces early atherosclerosis via enhanced foam cell expansion

Macrophages drive atherosclerotic plaque progression and rupture, hence attenuating their atherosclerosis-inducing properties holds promise for reducing coronary heart disease (CHD). Recent studies in mouse models have demonstrated that Tribbles 1 (Trib1) regulates macrophage phenotype and shows that Trib1 deficiency increases plasma cholesterol and triglyceride levels, suggesting that reduced TRIB1 expression mediates the strong genetic association between the TRIB1 locus and increased CHD risk in man. However, we report here that myeloid-specific Trib1 (mTrib1) deficiency reduces early atheroma formation and that mTrib1 transgene expression increases atherogenesis. Mechanistically, mTrib1 increased macrophage lipid accumulation and the expression of a critical receptor (OLR1), promoting oxidized low density lipoprotein uptake and the formation of lipid-laden foam cells. As TRIB1 and OLR1 RNA levels were also strongly correlated in human macrophages, we suggest that a conserved, TRIB1-mediated mechanism drives foam cell formation in atherosclerotic plaque and that inhibiting mTRIB1 could be used therapeutically to reduce CHD.

immunology↗