A viral RNA motif involved in signaling the initiation of translation on non-AUG codons
RNA
Authors: Angel Sanz, Miguel; Gonzalez Almela, Esther; Garcia-Moreno, Manuel; Isabel Marina, Ana; Carrasco, Luis
Abstract
Noncanonical translation, and particularly initiation on non-AUG codons, are frequently used by viral and cellular mRNAs during virus infection and disease. The Sindbis virus (SINV) subgenomic mRNA (sgRNA) constitutes a unique model system to analyze the translation of a capped viral mRNA without the participation of several initiation factors. Moreover, sgRNA can initiate translation even when the AUG initiation codon is replaced by other codons. Using SINV replicons, we examined the efficacy of different codons in place of AUG to direct the synthesis of the SINV capsid protein. The substitution of AUGby CUG was particularly efficient in promoting the incorporation of leucine or methionine in similar percentages at the amino terminus of the capsid protein. Additionally, valine could initiate translation when the AUG is replaced by GUG. The ability of sgRNA to initiate translation on non-AUG codons was dependent on the integrity of a downstream stable hairpin (DSH) structure located in the coding region. The structural requirements of this hairpin to signal the initiation site on the sgRNA were examined in detail. Of interest, a virus bearing CUG in place of AUG in the sgRNA was able to infect cells and synthesize significant amounts of capsid protein. This virus infects the human haploid cell line HAP1 and the double knockout variant that lacks eIF2A and eIF2D. Collectively, these findings indicate that leucine-tRNA or valine-tRNA can participate in the initiation of translation of sgRNA by a mechanism dependent on the DSH. This mechanism does not involve the action of eIF2, eIF2A, or eIF2D.
Mining the role of RECQL5 in gastric cancer and seeking potential regulatory network by bioinformatics analysis
EXPERIMENTAL AND MOLECULAR PATHOLOGY
Authors: Lin, Yijia; Chen, Honglei; Wang, Xinyou; Xiang, Jun; Wang, Huashe; Peng, Junsheng
Abstract
Aim: The role of RecQ protein-like 5 (RECQL5) in gastric carcinoma (GC) is still unclear. Here, we investigated the role of RECQL5 in human GC and its potential regulatory network via bioinformatics analysis. Methods: Bioinformatic analysis was performed using data in the Oncomine database, Kaplan- Meier Plotter online software, MethHC database, catalogue of somatic mutations in cancer (COSMIC), cbioportal database and String database. Then, we verified the association between RECQL5 expression and GC prognosis by immunohistochemistry (IHC). The independent prognostic factors were determined by Cox multivariate analysis. Results: It was found that both the mRNA and protein expression levels of RECQL5 were downregulated in GC samples (P < .05). Low RECQL5 expression indicated a poor prognosis in GC patients and is the independent prognostic factors for GC. No correlation between RECQL5 mRNA and DNA methylation was found using the MethHC database. The analysis of the COSMIC database showed a high proportion of missense mutation in GC. The functional enrichment analysis predicted that RECQL5 plays a role in DNA repair and cellular responses to DNA damage stimulus. RECQL5 might be enriched in homologous recombination pathways and Fanconi anemia pathway. Bioinformatics analysis identified 5 genes, namely POLR2D, POLR2G, DXO, KIN, and EIF2D, that were significantly correlated with RECQL5. Conclusion: The low expression of RECQL5 predicts poor overall survival in GC. RECQL5 may be a novel tumor suppressor for patients with GC.