bims-meprid 2022-05-01 papers

Issue of 2022‒05‒01
two papers selected by
Alessandro Carrer
Veneto Institute of Molecular Medicine

Life Sci Alliance. 2022 Aug;pii: e202201385. [Epub ahead of print]5(8):

Nutrient sensitive protein O-GlcNAcylation modulates the transcriptome through epigenetic mechanisms during embryonic neurogenesis.

Shama Parween, Thilina T Alawathugoda, Ashok D Prabakaran, S Thameem Dheen, Randall H Morse, Bright Starling Emerald, Suraiya A Ansari.

Protein O-GlcNAcylation is a dynamic, nutrient-sensitive mono-glycosylation deposited on numerous nucleo-cytoplasmic and mitochondrial proteins, including transcription factors, epigenetic regulators, and histones. However, the role of protein O-GlcNAcylation on epigenome regulation in response to nutrient perturbations during development is not well understood. Herein we recapitulated early human embryonic neurogenesis in cell culture and found that pharmacological up-regulation of O-GlcNAc levels during human embryonic stem cells' neuronal differentiation leads to up-regulation of key neurogenic transcription factor genes. This transcriptional de-repression is associated with reduced H3K27me3 and increased H3K4me3 levels on the promoters of these genes, perturbing promoter bivalency possibly through increased EZH2-Thr311 phosphorylation. Elevated O-GlcNAc levels also lead to increased Pol II-Ser5 phosphorylation and affect H2BS112O-GlcNAc and H2BK120Ub1 on promoters. Using an in vivo rat model of maternal hyperglycemia, we show similarly elevated O-GlcNAc levels and epigenetic dysregulations in the developing embryo brains because of hyperglycemia, whereas pharmacological inhibition of O-GlcNAc transferase (OGT) restored these molecular changes. Together, our results demonstrate O-GlcNAc mediated sensitivity of chromatin to nutrient status, and indicate how metabolic perturbations could affect gene expression during neurodevelopment.

DOI: https://doi.org/10.26508/lsa.202201385

Sci Immunol. 2022 Apr 29. 7(70): eabm8161

Succinate dehydrogenase/complex II is critical for metabolic and epigenetic regulation of T cell proliferation and inflammation.

Xuyong Chen, Benjamin Sunkel, Meng Wang, Siwen Kang, Tingting Wang, J N Rashida Gnanaprakasam, Lingling Liu, Teresa A Cassel, David A Scott, Ana M Muñoz-Cabello, Jose Lopez-Barneo, Jun Yang, Andrew N Lane, Gang Xin, Benjamin Z Stanton, Teresa W-M Fan, Ruoning Wang.

Effective T cell-mediated immune responses require the proper allocation of metabolic resources to sustain growth, proliferation, and cytokine production. Epigenetic control of the genome also governs T cell transcriptome and T cell lineage commitment and maintenance. Cellular metabolic programs interact with epigenetic regulation by providing substrates for covalent modifications of chromatin. By using complementary genetic, epigenetic, and metabolic approaches, we revealed that tricarboxylic acid (TCA) cycle flux fueled biosynthetic processes while controlling the ratio of succinate/α-ketoglutarate (α-KG) to modulate the activities of dioxygenases that are critical for driving T cell inflammation. In contrast to cancer cells, where succinate dehydrogenase (SDH)/complex II inactivation drives cell transformation and growth, SDH/complex II deficiency in T cells caused proliferation and survival defects when the TCA cycle was truncated, blocking carbon flux to support nucleoside biosynthesis. Replenishing the intracellular nucleoside pool partially relieved the dependence of T cells on SDH/complex II for proliferation and survival. SDH deficiency induced a proinflammatory gene signature in T cells and promoted T helper 1 and T helper 17 lineage differentiation. An increasing succinate/α-KG ratio in SDH-deficient T cells promoted inflammation by changing the pattern of the transcriptional and chromatin accessibility signatures and consequentially increasing the expression of the transcription factor, PR domain zinc finger protein 1. Collectively, our studies revealed a role of SDH/complex II in allocating carbon resources for anabolic processes and epigenetic regulation in T cell proliferation and inflammation.

DOI: https://doi.org/10.1126/sciimmunol.abm8161