July 21st, 2024
Recent Publications Harnessing the Power of Translatomics.
Every week we provide a digest of a small number of recent interesting papers in the field of translatomics.
In this week’s Sunday papers, Burgers et al. examines effects of HT and HHT effects on inflammation in a mouse peritonitis model and human endothelial cells, focusing on endothelial activation and leukocyte interactions. Hsieh et al. investigated the role of LIN28 in early cancer cells in mouse models. Aumailley et al. investigated the effects of ascorbate deficiency in Gulo-/- mice, which lack the enzyme Gulo, thus rely on dietary sources.
(Homo-)harringtonine prevents endothelial inflammation through IRF-1 dependent downregulation of VCAM1 mRNA expression and inhibition of cell adhesion molecule protein biosynthesis
Biomedicine & Pharmacotherapy, 2024
Burgers, L.D., Ciurus, S., Engel, P., Kuntschar, S., Raue, R., Kiprina, A., Primke, T., Schmid, T., Weigert, A., Schmidtko, A. and Fürst, R.
Acute inflammation defends the body against infections and injuries, involving cytokines like TNF that activate endothelial cells, leading to leukocyte recruitment via adhesion molecules ICAM-1 and VCAM-1. Chronic inflammation can cause severe diseases. Targeting endothelial interactions offers a potential therapeutic approach. Natural alkaloids harringtonine (HT) and homoharringtonine (HHT) known for anti-cancer effects, also show anti-inflammatory properties. HHT, FDA-approved for chronic myeloid leukemia, reduces inflammation in conditions like dermatitis and colitis. This study examines effects of HT and HHT effects on inflammation in a mouse peritonitis model and human endothelial cells, focusing on endothelial activation and leukocyte interactions.
Polysome profiling was used to investigate how HHT affects mRNA translation, particularly for ICAM1 mRNA, in human umbilical vein endothelial cells. HHT significantly reduced overall protein biosynthesis by 50% within 1 hour and sustained this reduction for 24 hours. Using polysome profiling and UV profiling, it was observed that HHT treatment shifted ICAM1 mRNA from actively translating late polysomes to non-translating monosomes, indicating a blockade of ICAM1 mRNA translation. This shift was confirmed by RT-qPCR. Similar effects were seen with SELE mRNA, suggesting HHT specifically impairs translation elongation for certain mRNAs while only partially reducing overall protein synthesis.
This study highlights HHT as an anti-inflammatory compound that effectively disrupts leukocyte-endothelial cell interactions by targeting the activation processes in endothelial cells.
Liver cancer initiation requires translational activation by an oncofetal regulon involving LIN28 proteins
The Journal of Clinical Investigation., 2024
Hsieh, M.H., Wei, Y., Li, L., Nguyen, L.H., Lin, Y.H., Yoon, J.M., Sun, X., Wang, X., Luo, X., Knutson, S.K. and Bracken, C.
In chronically inflamed tissues, tumor initiation repeatedly occurs, requiring cells to be oncogenically competent. While RNA binding proteins (RBPs) are less studied in cancer, their dysregulation promotes tumorigenesis. The LIN28 family, including Lin28a and Lin28b, enhances pluripotency, tissue growth, and carcinogenesis, inhibiting Let-7 microRNAs and influencing translation of numerous RNAs. Deletion of Lin28a/b impairs cancer initiation, with polysome profiling showing LIN28B boosts translation of specific RBPs. Using mouse models, this study reveals role of LIN28 in early cancer cells and underscores non-Let-7 translational mechanisms, suggesting anti-RBP strategies could prevent tumorigenesis.
Polysome profiling following LIN28B knockdown in Huh7 cells revealed a significant decrease in overall polysome abundance, indicating reduced translation activity. Among the LIN28B-regulated mRNA targets identified, 12 out of 15 showed a shift towards less active polysome fractions post-knockdown, suggesting decreased association with actively translating ribosomes. However, three targets (HNRNPF, HNRNPA2B1, SERBP1) did not exhibit changes in polysome distribution, indicating LIN28B’s selective influence on translational regulation among its mRNA interactors. Further, reporter assays revealed 8 target RBPs could restore NRASG12V/Tp53-driven cancer formation in Lin28a/Lin28b deficient mice. These LIN28B targets promote cancer initiation by enhancing protein synthesis. Thus, LIN28B, by enhancing the translation of specific RBPs within an RNP regulon, plays a crucial role in liver tumor initiation.
These studies underscore the significance of translational mechanisms independent of Let-7 regulation downstream of LIN28, suggesting the potential for anti-RBP strategies to prevent tumorigenesis.
Combined transcriptomics and proteomics unveil the impact of vitamin C in modulating specific protein abundance in the mouse liver
Biological Research, 2024
Vitamin C (ascorbate) is a water-soluble antioxidant that plays a vital role as a cofactor in numerous biosynthetic and regulatory enzyme processes. Unlike humans, mice can produce vitamin C because they possess the enzyme gulonolactone oxidase (Gulo). The authors investigated the effects of ascorbate deficiency in Gulo-/- mice, which lack the enzyme Gulo, thus rely on dietary sources.
In the study, Gulo-/- mice given either sub-optimal or optimal ascorbate levels in their drinking water. Liver tissues from both female and male mice were collected at four months of age for analysis. Integrative omics analysis, including transcriptomics and proteomics, of whole liver tissues was conducted. Additionally, polysome profiling and RNA-seq, were used to provide insights into translation-level alterations of specific genes. This approach aimed to elucidate how ascorbate deficiency influences gene and protein expression, particularly in hepatic metabolic and stress response processes, across both male and female mice.
In ascorbate-deficient Gulo-/- mice, polysome profiling showed no significant differences in overall translation between deficient and supplemented groups. However, targeted RT-PCR revealed reduced association of mannose-binding lectin 2 (Mbl2) mRNA with heavy polysomes in supplemented mice, correlating with lower Mbl2 protein levels. RNA-seq identified distinct transcriptomic and proteomic profiles between sexes, impacting six biological processes.
These findings demonstrate that ascorbate plays a dual role in modulating gene expression, affecting both transcriptional and post-transcriptional mechanisms. Integrating RNA-seq with polysome profiling provided a comprehensive understanding of how vitamin C regulates translation. This study advances our understanding of cellular regulatory functions of vitamin C, shedding light on its implications for health and disease.