Showing papers by "Théophile Ohlmann published in 2022"
TL;DR: In this article , the authors show that 5-fluorouracil (5-FU) treatment leads to the production of fluorinated ribosomes exhibiting altered translational activities and that sustained translation of IGF-1R mRNA, which encodes one of the most potent cell survival effectors, promotes the survival of 5-FU-treated colorectal cancer cells.
Abstract: Abstract Mechanisms of drug-tolerance remain poorly understood and have been linked to genomic but also to non-genomic processes. 5-fluorouracil (5-FU), the most widely used chemotherapy in oncology is associated with resistance. While prescribed as an inhibitor of DNA replication, 5-FU alters all RNA pathways. Here, we show that 5-FU treatment leads to the production of fluorinated ribosomes exhibiting altered translational activities. 5-FU is incorporated into ribosomal RNAs of mature ribosomes in cancer cell lines, colorectal xenografts, and human tumors. Fluorinated ribosomes appear to be functional, yet, they display a selective translational activity towards mRNAs depending on the nature of their 5′-untranslated region. As a result, we find that sustained translation of IGF-1R mRNA, which encodes one of the most potent cell survival effectors, promotes the survival of 5-FU-treated colorectal cancer cells. Altogether, our results demonstrate that “man-made” fluorinated ribosomes favor the drug-tolerant cellular phenotype by promoting translation of survival genes.
12 citations
TL;DR: It was shown that selenium had no significant effect on HIV-1 protein production nor on infectivity, but slightly reduced the percentage of infected cells in a Jurkat cell line and isolated primary CD4 T cells, and in response to HIV- 1 infection, the selenoproteome was slightly altered.
Abstract: The infection of CD4 T-lymphocytes with human immunodeficiency virus (HIV), the etiological agent of acquired immunodeficiency syndrome (AIDS), disrupts cellular homeostasis, increases oxidative stress and interferes with micronutrient metabolism. Viral replication simultaneously increases the demand for micronutrients and causes their loss, as for selenium (Se). In HIV-infected patients, selenium deficiency was associated with a lower CD4 T-cell count and a shorter life expectancy. Selenium has an important role in antioxidant defense, redox signaling and redox homeostasis, and most of these biological activities are mediated by its incorporation in an essential family of redox enzymes, namely the selenoproteins. Here, we have investigated how selenium and selenoproteins interplay with HIV infection in different cellular models of human CD4 T lymphocytes derived from established cell lines (Jurkat and SupT1) and isolated primary CD4 T cells. First, we characterized the expression of the selenoproteome in various human T-cell models and found it tightly regulated by the selenium level of the culture media, which was in agreement with reports from non-immune cells. Then, we showed that selenium had no significant effect on HIV-1 protein production nor on infectivity, but slightly reduced the percentage of infected cells in a Jurkat cell line and isolated primary CD4 T cells. Finally, in response to HIV-1 infection, the selenoproteome was slightly altered.
6 citations
TL;DR: Interestingly, the translation initiation mechanism on the SARS-CoV-2 gRNA 5′UTR requires the cap structure and the components of the eIF4F complex but showed no dependence in the presence of the poly(A) tail in vitro.
Abstract: The SARS-CoV-2 infection generates up to nine different sub-genomic mRNAs (sgRNAs), in addition to the genomic RNA (gRNA). The 5′UTR of each viral mRNA shares the first 75 nucleotides (nt.) at their 5′end, called the leader, but differentiates by a variable sequence (0 to 190 nt. long) that follows the leader. As a result, each viral mRNA has its own specific 5′UTR in term of length, RNA structure, uORF and Kozak context; each one of these characteristics could affect mRNA expression. In this study, we have measured and compared translational efficiency of each of the ten viral transcripts. Our data show that most of them are very efficiently translated in all translational systems tested. Surprisingly, the gRNA 5′UTR, which is the longest and the most structured, was also the most efficient to initiate translation. This property is conserved in the 5′UTR of SARS-CoV-1 but not in MERS-CoV strain, mainly due to the regulation imposed by the uORF. Interestingly, the translation initiation mechanism on the SARS-CoV-2 gRNA 5′UTR requires the cap structure and the components of the eIF4F complex but showed no dependence in the presence of the poly(A) tail in vitro. Our data strongly suggest that translation initiation on SARS-CoV-2 mRNAs occurs via an unusual cap-dependent mechanism.
4 citations
TL;DR: Analysis of ribosome profiling reads from viral transcripts reveals extensive and productive non-AUG translation of small peptides from multiple upstream open reading-frames located in the 5’ long terminal repeat, which elicit specific T cell responses in HIV-infected individuals.
Abstract: Human immunodeficiency virus type-1 (HIV-1) is a complex retrovirus which relies on alternative splicing, translational and post-translational mechanisms to produce more than 15 functional proteins from its single ∼10kb transcriptional unit. Here, we have applied ribosome profiling and nascent protein labeling at different time points during infection of CD4+ T lymphocytes to characterize the translational landscape of cellular and viral transcripts during the course of infection. Our results indicate a strong impact of viral infection on host cellular transcript levels but a modest impact on global translation rates. Analysis of ribosome profiling reads from viral transcripts reveals extensive and productive non-AUG translation of small peptides from multiple upstream open reading-frames (uORFs) located in the 5’ long terminal repeat. Remarkably, these uORFs derived peptides elicit specific T cell responses in HIV-infected individuals. uORFs are conserved among other retroviruses and, together with the TAR sequence, condition the dependency on DDX3 for efficient translation of the main viral open-reading frames.
3 citations