Translation initiation downstream from annotated start codons in human mRNAs coevolves with the Kozak context

Eukaryotic translation initiation involves preinitiation ribosomal complex 5′ -to-3′ directional probing of mRNA for codons suitable for starting protein synthesis. The recognition of codons as starts depends on the codon identity and on its immediate nucleotide context known as Kozak context. When the context is weak (i.e., nonoptimal), leaky scanning takes place during which a fraction of ribosomes continues the mRNA probing. We explored the relationship between the context of AUG codons annotated as starts of protein-coding sequences and the next AUG codon occurrence. We found that AUG codons downstream from weak starts occur in the same frame more frequently than downstream from strong starts. We suggest that evolutionary selection on in-frame AUGs downstream from weak start codons is driven by the advantage of the reduction of wasteful out-of-frame product synthesis and also by the advantage of producing multiple proteoforms from certain mRNAs. We confirmed translation initiation downstream from weak start codons using ribosome profiling data. We also tested translation of alternative start codons in 10 specific human genes using reporter constructs. In all tested cases, initiation at downstream start codons was more productive than at the annotated ones. In most cases, optimization of Kozak context did not completely abolish downstream initiation, and in the specific example of CMPK1 mRNA, the optimized start remained unproductive. Collectively, our work reveals previously uncharacterized forces shaping the evolution of protein-coding genes and points to the plurality of translation initiation and the existence of sequence features influencing start codon selection, other than Kozak context.Russian Science Foundation (RSF) 20-14-00121Science Foundation Ireland 210692/Z/18/ZScience Foundation Ireland 12/RC/2276_P2Erasmus+ ProgrammePlan Propio de Investigacion 2019 de la Universidad de GranadaMinistry of Economy of Spain DPI2017-84439-REuropean Union (EU) DPI2017-84439-

BCL7A is silenced by hypermethylation to promote acute myeloid leukemia

The online version contains supplementary material available at https:// doi. org/ 10. 1186/ s40364‑ 023‑ 00472‑x. Additional file 1: Supplementary Figure 1. Diagram displaying CpG‑ methylation status around the BCL7A TSS. Genomic DNA from the NB4 cell line was subjected to bisulfite conversion and used for subsequent TA‑ cloning. Supplementary Figure 2. Schematic representation of the differ‑ ent lentiviral plasmids used in the experimental procedures. The specific region of the long isoform of BCL7A is colored in blue. Supplementary Figure 3. Western blot including the Decitabine (DAC) treatment over the NB4 cell line shown in Fig. 2c. Supplementary Figure 4. Protein‑protein interactions between BCL7A and SMARCA4 as determined by Mashtalir et al (2020). Supplementary Figure 5. DepMap AML cell lines collection data showing BCL7A Methylation Fraction (1kb upstream TSS) vs BCL7Aex‑ pression level. NB4 and M07e are marked. Supplementary Figure 6. Competition cell growth effect of BCL7A expression restoration on in vitro proliferation. Supplementary Table 1. Additional file 2: Supplementary Table 2. Differential expression analysis resultsP.P.M.’s laboratory is funded by Consejería de Universidad, Investigación e Innovación de la Junta de Andalucía and FEDER (P20‑00688), Aula de Investigación sobre la Leucemia infantil: Heroes contra la Leucemia, the Ministry of Science and Innovation of Spain (grant PID2021‑126111OB‑I00), Junta de Andalucía (grants PIGE‑0440–2019, PI‑0135–2020), the University of Granada (grants B‑CTS‑126‑UGR18, B‑CTS‑480‑UGR20, and E‑CTS‑304‑UGR20), and the Spanish Association for Cancer Research (LABORATORY‑AECC‑2018). J.R.P‑M, A.A, and M.S.B‑C were supported by fellowships FPU18/03709, FPU17/00067, and FPU19/00576 respectively funded by the Spanish Ministry of Science, Innovation and UniversitiesBackground Recent massive sequencing studies have revealed that SWI/SNF complexes are among the most fre‑ quently altered functional entities in solid tumors. However, the role of SWI/SNF in acute myeloid leukemia is poorly understood. To date, SWI/SNF complexes are thought to be oncogenic in AML or, at least, necessary to support leuke‑ mogenesis. However, mutation patterns in SWI/SNF genes in AML are consistent with a tumor suppressor role. Here, we study the SWI/SNF subunit BCL7A, which has been found to be recurrently mutated in lymphomas, but whose role in acute myeloid malignancies is currently unknown. Methods Data mining and bioinformatic approaches were used to study the mutational status of BCL7A and the correlation between BCL7A expression and promoter hypermethylation. Methylation‑specific PCR, bisulfite sequenc‑ ing, and 5‑aza‑2’‑deoxycytidine treatment assays were used to determine if BCL7A expression was silenced due to promoter hypermethylation. Cell competition assays after BCL7A expression restoration were used to assess the role of BCL7A in AML cell line models. Differential expression analysis was performed to determine pathways and genes altered after BCL7A expression restoration. To establish the role of BCL7A in tumor development in vivo, tumor growth was compared between BCL7A‑expressing and non‑expressing mouse xenografts using in vivo fluorescence imaging. Results BCL7A expression was inversely correlated with promoter methylation in three external cohorts: TCGA‑LAML (N = 160), TARGET‑AML (N = 188), and Glass et al. (2017) (N = 111). The AML‑derived cell line NB4 silenced the BCL7A expression via promoter hypermethylation. Ectopic BCL7A expression in AML cells decreased their competitive ability compared to control cells. Additionally, restoration of BCL7A expression reduced tumor growth in an NB4 mouse xenograft model. Also, differential expression analysis found that BCL7A restoration altered cell cycle pathways and modified significantly the expression of genes like HMGCS1, H1-0, and IRF7 which can help to explain its tumor sup‑ pressor role in AML. Conclusions BCL7A expression is silenced in AML by promoter methylation. In addition, restoration of BCL7A expres‑ sion exerts tumor suppressor activity in AML cell lines and xenograft models.Consejería de Universidad, Investigación e Innovación de la Junta de Andalucía and FEDER (P20‑00688)Ministry of Science and Innovation of Spain (grant PID2021‑126111OB‑I00)Junta de Andalucía (grants PIGE‑0440–2019, PI‑0135–2020)University of Granada (B‑CTS‑126‑UGR18, B‑CTS‑480‑UGR20, E‑CTS‑304‑UGR20)Spanish Association for Cancer Research (LABORATORY‑AECC‑2018)Spanish Ministry of Science, Innovation and Universities FPU18/03709, FPU17/00067, FPU19/0057

Additional file 1 of Activation-induced cytidine deaminase causes recurrent splicing mutations in diffuse large B-cell lymphoma

Supplementary Material 1

Translation initiation downstream from annotated start codons in human mRNAs coevolves with the Kozak context

Eukaryotic translation initiation involves preinitiation ribosomal complex 5'-to-3' directional probing of mRNA for codons suitable for starting protein synthesis. The recognition of codons as starts depends on the codon identity and on its immediate nucleotide context known as Kozak context. When the context is weak (i.e., nonoptimal), leaky scanning takes place during which a fraction of ribosomes continues the mRNA probing. We explored the relationship between the context of AUG codons annotated as starts of protein-coding sequences and the next AUG codon occurrence. We found that AUG codons downstream from weak starts occur in the same frame more frequently than downstream from strong starts. We suggest that evolutionary selection on in-frame AUGs downstream from weak start codons is driven by the advantage of the reduction of wasteful out-of-frame product synthesis and also by the advantage of producing multiple proteoforms from certain mRNAs. We confirmed translation initiation downstream from weak start codons using ribosome profiling data. We also tested translation of alternative start codons in 10 specific human genes using reporter constructs. In all tested cases, initiation at downstream start codons was more productive than at the annotated ones. In most cases, optimization of Kozak context did not completely abolish downstream initiation, and in the specific example of CMPK1 mRNA, the optimized start remained unproductive. Collectively, our work reveals previously uncharacterized forces shaping the evolution of protein-coding genes and points to the plurality of translation initiation and the existence of sequence features influencing start codon selection, other than Kozak context

Multi-omic alterations of the SWI/SNF complex define a clinical subgroup in lung adenocarcinoma.

SWI/SNF complexes are major targets of mutations in cancer. Here, we combined multiple "-omics" methods to assess SWI/SNF composition and aberrations in LUAD. Mutations in lung SWI/SNF subunits were highly recurrent in our LUAD cohort (41.4%), and over 70% of the mutations were predicted to have functional impact. Furthermore, SWI/SNF expression in LUAD suffered an overall repression that could not be explained exclusively by genetic alterations. Finally, SWI/SNF mutations were associated with poorer overall survival in TCGA-LUAD. We propose SWI/SNF-mutant LUAD as a separate clinical subgroup with practical implications

Risk of COVID-19 after natural infection or vaccinationResearch in context

Summary: Background: While vaccines have established utility against COVID-19, phase 3 efficacy studies have generally not comprehensively evaluated protection provided by previous infection or hybrid immunity (previous infection plus vaccination). Individual patient data from US government-supported harmonized vaccine trials provide an unprecedented sample population to address this issue. We characterized the protective efficacy of previous SARS-CoV-2 infection and hybrid immunity against COVID-19 early in the pandemic over three-to six-month follow-up and compared with vaccine-associated protection. Methods: In this post-hoc cross-protocol analysis of the Moderna, AstraZeneca, Janssen, and Novavax COVID-19 vaccine clinical trials, we allocated participants into four groups based on previous-infection status at enrolment and treatment: no previous infection/placebo; previous infection/placebo; no previous infection/vaccine; and previous infection/vaccine. The main outcome was RT-PCR-confirmed COVID-19 >7–15 days (per original protocols) after final study injection. We calculated crude and adjusted efficacy measures. Findings: Previous infection/placebo participants had a 92% decreased risk of future COVID-19 compared to no previous infection/placebo participants (overall hazard ratio [HR] ratio: 0.08; 95% CI: 0.05–0.13). Among single-dose Janssen participants, hybrid immunity conferred greater protection than vaccine alone (HR: 0.03; 95% CI: 0.01–0.10). Too few infections were observed to draw statistical inferences comparing hybrid immunity to vaccine alone for other trials. Vaccination, previous infection, and hybrid immunity all provided near-complete protection against severe disease. Interpretation: Previous infection, any hybrid immunity, and two-dose vaccination all provided substantial protection against symptomatic and severe COVID-19 through the early Delta period. Thus, as a surrogate for natural infection, vaccination remains the safest approach to protection. Funding: National Institutes of Health

Risk of COVID-19 after natural infection or vaccinationResearch in context

Background: While vaccines have established utility against COVID-19, phase 3 efficacy studies have generally not comprehensively evaluated protection provided by previous infection or hybrid immunity (previous infection plus vaccination). Individual patient data from US government-supported harmonized vaccine trials provide an unprecedented sample population to address this issue. We characterized the protective efficacy of previous SARS-CoV-2 infection and hybrid immunity against COVID-19 early in the pandemic over three-to six-month follow-up and compared with vaccine-associated protection. Methods: In this post-hoc cross-protocol analysis of the Moderna, AstraZeneca, Janssen, and Novavax COVID-19 vaccine clinical trials, we allocated participants into four groups based on previous-infection status at enrolment and treatment: no previous infection/placebo; previous infection/placebo; no previous infection/vaccine; and previous infection/vaccine. The main outcome was RT-PCR-confirmed COVID-19 >7–15 days (per original protocols) after final study injection. We calculated crude and adjusted efficacy measures. Findings: Previous infection/placebo participants had a 92% decreased risk of future COVID-19 compared to no previous infection/placebo participants (overall hazard ratio [HR] ratio: 0.08; 95% CI: 0.05–0.13). Among single-dose Janssen participants, hybrid immunity conferred greater protection than vaccine alone (HR: 0.03; 95% CI: 0.01–0.10). Too few infections were observed to draw statistical inferences comparing hybrid immunity to vaccine alone for other trials. Vaccination, previous infection, and hybrid immunity all provided near-complete protection against severe disease. Interpretation: Previous infection, any hybrid immunity, and two-dose vaccination all provided substantial protection against symptomatic and severe COVID-19 through the early Delta period. Thus, as a surrogate for natural infection, vaccination remains the safest approach to protection. Funding: National Institutes of Health