Biology subjects

Contreras, R.

Publications and source records attributed to Contreras, R..

4 recordsLinked to original sources

bioRxiv2024

Chromatin regulator HELLS mediates SSB repair and responses to DNA alkylation damage.

The SNF2 family chromatin remodeler HELLS has emerged as an important regulator of cell proliferation, genome stability, and several cancer pathways. Significant upregulation of HELLS has been reported in 33 human cancer types. While HELLS has been implicated in DNA damage response, its function in DNA repair is poorly understood. Here we report a new regulatory link between HELLS and single-strand break (SSB) repair in cellular responses to DNA alkylation damage. We found that loss of HELLS impairs SSB repair, and selectively sensitizes cells to DNA alkylating agents and PARP inhibitors (PARPi). Furthermore, we found that HELLS is co-expressed with PARP1 in cancer cells, and its loss is synthetic lethal with homologous recombination deficiency (HRD). This work unveils new functions of HELLS in modulating SSB repair and responses to clinically relevant DNA alkylation damage, thus offering new insights into the potential therapeutic value of targeting HELLS in cancer. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=158 SRC="FIGDIR/small/629292v2_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@2bbd3eorg.highwire.dtl.DTLVardef@1956f14org.highwire.dtl.DTLVardef@1afcb7corg.highwire.dtl.DTLVardef@58504c_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2020

A mesocosm experiment in ecological physiology: adaptive modulation of energy budget in a hibernating marsupial under chronic caloric restriction

During the last sixty years, mammalian hibernation (i.e., seasonal torpor) has been interpreted as a physiological adaptation for energy economy. However -and crucially for validating this idea - direct field comparisons of energy expenditure in hibernating and active free-ranging animals are scarce. Using replicated mesocosms and a combination of energy budgeting approaches (i.e., doubly labelled water, rates of CO2 production and food intake), we experimentally manipulated energy availability and quantified net energy costs of hibernation in a marsupial. We hypothesized that, when facing chronic caloric restriction (CCR), a hibernator should maximize torpor use for compensating the energetic deficit, compared to ad libitum fed individuals (=controls). However, intensifying torpor duration at low temperatures could increase other burdens (e.g., cost of rewarming, freezing risk). In order to explore this trade-off, we followed the complete hibernation cycle of the relict marsupial Dromiciops gliroides, and estimated its total energy requirements, and compared this with a control condition. Our results revealed: (1) that energy restricted animals, instead of promoting heat conservation strategies during hibernation (e.g., social clustering and thermoregulation), maximized torpor use and saved just enough energy to cover the deficit, and (2) that hibernation represents a net energy saving of 51% compared with animals that remained active. This work provides compelling evidence of a fine-tuning use of hibernation in response to food availability and presents the first direct estimation of energy savings by hibernation encompassing the total hibernation cycle.

ecology↗

bioRxiv2020

Off-target glycans encountered along the synthetic biology route towards humanized N-glycans in Pichia pastoris

BackgroundThe glycosylation pathways of several eukaryotic protein expression hosts are being engineered to enable the production of therapeutic glycoproteins with humanized application-customized glycan structures. In several expression hosts, this has been quite successful, but one caveat is that the new N-glycan structures inadvertently might be substrates for one or more of the multitude of endogenous glycosyltransferases in such heterologous background. This then results in the formation of novel, undesired glycan structures, which often remain insufficiently characterized. ResultsWhen expressing mouse interleukin-22 (mIL-22) in a Pichia pastoris (syn. Komagataella phaffi) GlycoSwitchM5 strain which had been optimized to produce Man5GlcNAc2 N-glycans, glycan profiling revealed two major species: Man5GlcNAc2 and an unexpected, partially -mannosidase-resistant structure. A detailed structural analysis using exoglycosidase sequencing, mass spectrometry, linkage analysis and NMR, revealed that this novel glycan was Man5GlcNAc2 modified with a Glc-1,2-Man{beta}-1,2-Man{beta}-1,3-Glc-1,3-R tetra-saccharide. Also the biosynthetic intermediates of this off-target modification were detected. Expression of a Golgi-targeted GlcNAc Transferase-I strongly inhibited the formation of this novel modification, resulting in more homogeneous modification with the targeted GlcNAcMan5GlcNAc2 structure. We have also observed the off-target glycan on other glycoproteins produced in the GlycoSwitchM5 strain. This illustrates the intricacies of Golgi glycosylation pathways and cautions that the use of glyco-engineered expression host cells should always be accompanied by detailed glycan analysis of the particular therapeutic proteins being produced. ConclusionsOur findings reinforce accumulating evidence that robustly customizing the N-glycosylation pathway in Pichia pastoris to produce particular human-type structures is still an incompletely solved synthetic biology challenge, which will require further innovation to enable safe glycoprotein pharmaceutical production.

synthetic biology↗

bioRxiv2018

Expression of a glucomannan mannosyltransferase gene (GMMT) from Aloe vera is induced by water deficit and abscisic acid.

HighlightGMMT (a possible CSLA9) from Aloe vera is upregulated during water stress. Aloe vera GMMT expression is also induced by exogenous application of the plant stress hormone abscisic acid (ABA) in non-water-stressed plants.\n\nSummaryIn Aloe barbadensis Miller (Aloe vera), a xerophytic crassulacean acid metabolism (CAM) plant, the main polysaccharide of the gel present in the leaves is an acetylated glucomannan named acemannan. This polysaccharide is responsible for the plant succulence, helping it to retain water. In this study we determined using polysaccharide analysis by carbohydrate gel electrophoresis (PACE) that the acemannan is a glucomannan without galactose side branches. We also investigated the expression of the gene responsible for acemannan backbone synthesis, encoding a glucomannan mannosyltransferase (GMMT). It was found by in silico analyses that the GMMT gene belongs to the cellulose synthase like A type-9 (CSLA9) subfamily. Using RT-qPCR it was found that the expression of GMMT increased in Aloe vera plants subjected to water stress. This expression correlates with an increase of endogenous ABA levels, suggesting that the gene expression could be regulated by ABA. To corroborate this hypothesis, exogenous ABA was applied to non-water-stressed plants, increasing the expression of GMMT significantly 48 h after ABA treatment.

plant biology↗