RELA governs a network of islet-specific metabolic genes necessary for beta cell function

tRNA-derived fragment 3031B regulates human anterior cruciate ligament cell proliferation and survival by targeting RELA

tRNA-derived fragments (tRFs) are novel short noncoding RNAs that play pivotal roles in cell proliferation and survival. However, knowledge of the biological roles of tRFs in anterior cruciate ligament (ACL) cells is limited. Here, we intended to investigate the function of tRF-3031B in ACL cell. We used the tRF and tiRNA array to analyze tRF and tiRNA expression profiles in osteoarthritis (OA) ACL cells and normal ACL cells, and qRT-PCR and fluorescence in situ hybridization (FISH) were used to determine tRF-3031B expression. The results showed that tRF-3031B was expressed at low levels in OA ACL and Interleukin-1β (IL-1β) treated ACL cells. We found that RELA was the target of tRF-3031B. When ACL cells were transfected with tRF-3031B mimics, RELA expression was suppressed, whereas transfection with tRF-3031B inhibitors had the opposite effect. The rescue and dual-luciferase reporter assays showed that tRF-3031B silenced the RELA expression by binding to its untranslated region (3'-UTR). Hence, this study showed the novel function of tRF-3031B in regulating ACL cell proliferation and survival by targeting RELA, and these findings may offer a new direction for the study of ACL degeneration and pathophysiological of OA.

Repression of latent NF-κB enhancers by PDX1 regulates β cell functional heterogeneity

Interactions between lineage-determining and activity-dependent transcription factors determine single-cell identity and function within multicellular tissues through incompletely known mechanisms. By assembling a single-cell atlas of chromatin state within human islets, we identified β cell subtypes governed by either high or low activity of the lineage-determining factor pancreatic duodenal homeobox-1 (PDX1). β cells with reduced PDX1 activity displayed increased chromatin accessibility at latent nuclear factor κB (NF-κB) enhancers. Pdx1 hypomorphic mice exhibited de-repression of NF-κB and impaired glucose tolerance at night. Three-dimensional analyses in tandem with chromatin immunoprecipitation (ChIP) sequencing revealed that PDX1 silences NF-κB at circadian and inflammatory enhancers through long-range chromatin contacts involving SIN3A. Conversely, Bmal1 ablation in β cells disrupted genome-wide PDX1 and NF-κB DNA binding. Finally, antagonizing the interleukin (IL)-1β receptor, an NF-κB target, improved insulin secretion in Pdx1 hypomorphic islets. Our studies reveal functional subtypes of single β cells defined by a gradient in PDX1 activity and identify NF-κB as a target for insulinotropic therapy.

Metabolic Enzymes in Viral Infection and Host Innate Immunity

Metabolic enzymes are central players for cell metabolism and cell proliferation. These enzymes perform distinct functions in various cellular processes, such as cell metabolism and immune defense. Because viral infections inevitably trigger host immune activation, viruses have evolved diverse strategies to blunt or exploit the host immune response to enable viral replication. Meanwhile, viruses hijack key cellular metabolic enzymes to reprogram metabolism, which generates the necessary biomolecules for viral replication. An emerging theme arising from the metabolic studies of viral infection is that metabolic enzymes are key players of immune response and, conversely, immune components regulate cellular metabolism, revealing unexpected communication between these two fundamental processes that are otherwise disjointed. This review aims to summarize our present comprehension of the involvement of metabolic enzymes in viral infections and host immunity and to provide insights for potential antiviral therapy targeting metabolic enzymes.