Biology subjects

Wong, D. C.

Publications and source records attributed to Wong, D. C..

3 recordsLinked to original sources

bioRxiv2022

Circadian regulation of protein turnover and proteome renewal

Although costly to maintain, protein homeostasis is indispensable for normal cellular function and long-term health. In mammalian cells and tissues, daily variation in global protein synthesis has been observed, but its utility and consequences for proteome integrity are not fully understood. Using several different pulse-labelling strategies, here we gain direct insight into the relationship between protein synthesis and abundance proteome-wide. We show that protein degradation varies in-phase with protein synthesis, facilitating rhythms in turnover rather than abundance. This results in daily consolidation of proteome renewal whilst minimising changes in composition. Coupled rhythms in synthesis and turnover are especially salient to the assembly of macromolecular protein complexes, particularly the ribosome, the most abundant species of complex in the cell. Daily turnover and proteasomal degradation rhythms render cells and mice more sensitive to proteotoxic stress at specific times of day, potentially contributing to daily rhythms in the efficacy of proteasomal inhibitors against cancer. Our findings suggest that circadian rhythms function to minimise the bioenergetic cost of protein homeostasis through temporal consolidation of protein turnover.

cell biology↗

bioRxiv2022

Biosynthesis and apoplast accumulation of the apocarotenoid pigment azafrin in parasitizing roots of Escobedia grandiflora

O_LIThe herbaceous hemiparasite Escobedia grandiflora (Orobanchaceae) is used in traditional medicine in the Andean region. Their roots accumulate an orange pigment with a significant relevance as a cooking dye that exhibits antioxidant and cardioprotective properties. C_LIO_LIThe present work combined metabolic and cytological analyses with de novo transcriptome assembly, gene expression studies, and phylogenetic analyses to confirm the chemical identity of the pigment and investigate its biosynthesis and function in Escobedia roots. C_LIO_LIThe pigment was conclusively shown to be azafrin, an apocarotenoid likely derived from the cleavage of {beta}-carotene. Candidate genes for the production of azafrin in Escobedia roots are proposed based on RNA-seq supported by RT-qPCR and phylogeny reconstruction analyses. In particular, our data suggest that azafrin production relies a carotenoid cleavage dioxygenase (CCD) different from CCD7 and similar to CCD4 enzymes. We also show that azafrin is delivered to the root apoplast and that it accumulates in the area where the Escobedia haustorium contacts the hosts root, suggesting a role of azafrin in the parasitization process. C_LIO_LIAltogether, our work represents an unprecedented step forward in our understanding of the Escobedia parasitization system, but it also provides vital information towards the eventual domestication of this valuable medicinal plant. C_LI

plant biology↗

bioRxiv2021

Pre-existing chromatin accessibility and gene expression differences among naïve CD4+ T cells influence effector potential

CD4+ T cells have a remarkable potential to differentiate into diverse effector lineages following activation. Here, we probed the heterogeneity present among naive CD4+ T cells before encountering their cognate antigen to ask whether their effector potential is modulated by pre-existing transcriptional and epigenetic differences. Using single-cell RNA sequencing, we showed that key drivers of variability are genes involved in T cell receptor (TCR) signaling. Using CD5 expression as a read-out of the strength of tonic TCR interactions with self-peptide MHC, and sorting on the ends of this self-reactivity spectrum, we find that pre-existing transcriptional differences among naive CD4+ T cells impact follicular helper cell (TFH) versus non-TFH effector lineage choice. Moreover, our data implicate TCR signal strength during thymic development in establishing differences in naive CD4 T cell chromatin landscapes that ultimately shape their effector potential.

immunology↗