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A second eukaryotic group with mitochondrion-encoded tmRNA: in silico identification and experimental confirmation.

ABSTRACT: In bacteria, stalled ribosomes are rescued by transfer-mRNA (tmRNA) that catalyzes two steps. First, a non-encoded alanine is added to the incomplete polypeptide chain by the tRNA (Ala) -like portion of tmRNA, and second, the ribosome switches to the mRNA-like domain of tmRNA, thus resuming protein synthesis. Mitochondrial DNA (mtDNA)-encoded mt-tmRNA is so far only known from jakobid protists, but we posit that the corresponding ssrA gene may also reside in other mtDNAs. Here we present a highly sensitive covariance model built from jakobid ssrA genes that identifies previously unrecognized ssrA homologs in mtDNAs of oomycetes. These genes, located in previously unassigned genomic regions, are circular permuted as in ?-Protobacteria, implying that pre-tmRNA is processed and the two pieces are held together by non-covalent interactions. RNA-Seq data from Phytophthora sojae confirm predicted processing sites as well as post-transcriptional addition of 3' CCA, a prerequisite for tmRNAs to be charged with alanine by alanyl-tRNA synthetase. Structure modeling of oomycete tmRNAs infers that the mRNA-like domain is lacking as in jakobids. Features of mitochondrial tmRNAs include the G-U pair at position three of the acceptor stem, a hallmark of bacterial tmRNAs, and a T-loop sequence that differs from that of standard tRNAs and most bacterial tmRNAs, forming alternative, virtually isosteric tertiary interactions with the D-loop. The anticodon stem has two additional G-A base pairs formed between the D-loop and the variable region, shortening the length of the variable region to a single nucleotide.

SUBMITTER: Hafez M

PROVIDER: S-EPMC3849159 | biostudies-literature | 2013 Jul

REPOSITORIES: biostudies-literature

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A second eukaryotic group with mitochondrion-encoded tmRNA: in silico identification and experimental confirmation.

Hafez Mohamed M Burger Gertraud G Steinberg Sergey V SV Lang B Franz BF

RNA biology 20130617 7

In bacteria, stalled ribosomes are rescued by transfer-mRNA (tmRNA) that catalyzes two steps. First, a non-encoded alanine is added to the incomplete polypeptide chain by the tRNA (Ala) -like portion of tmRNA, and second, the ribosome switches to the mRNA-like domain of tmRNA, thus resuming protein synthesis. Mitochondrial DNA (mtDNA)-encoded mt-tmRNA is so far only known from jakobid protists, but we posit that the corresponding ssrA gene may also reside in other mtDNAs. Here we present a highl ...[more]

PMID: 23823571

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Project description:BackgroundEsophageal squamous cell carcinoma (ESCC) as the main subtype of esophageal cancer (EC) is a leading cause of cancer-related death worldwide. Despite advances in early diagnosis and clinical management, the long-term survival of ESCC patients remains disappointing, due to a lack of full understanding of the molecular mechanisms.MethodsIn order to identify the differentially expressed genes (DEGs) in ESCC, the microarray datasets GSE20347 and GSE26886 from Gene Expression Omnibus (GEO) database were analyzed. The enrichment analyses of gene ontology (GO) terms, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and Gene Set Enrichment Analysis (GSEA) were performed for the DEGs. The protein-protein interaction (PPI) network of these DEGs was constructed using the Cytoscape software based on the STRING database to select as hub genes for weighted co-expression network analysis (WGCNA) with ESCC samples from TCGA database.ResultsA total of 746 DEGs were commonly shared in the two datasets including 286 upregulated genes and 460 downregulated genes in ESCC. The DEGs were enriched in biological processes such as extracellular matrix organization, proliferation and keratinocyte differentiation, and were enriched in biological pathways such as ECM-receptor interaction and cell cycle. GSEA analysis also indicated the enrichment of upregulated DEGs in cell cycle. The 40 DEGs were selected as hub genes. The MEblack module was found to be enriched in the cell cycle, Spliceosome, DNA replication and Oocyte meiosis. Among the hub genes correlated with MEblack module, GSEA analysis indicated that DEGs of TCGA samples with DLGAP5 upregulation was enriched in cell cycle. Moreover, the highly endogenous expression of DLGAP5 was confirmed in ESCC cells. DLGAP5 knockdown significantly inhibited the proliferation of ESCC cells.ConclusionsDEGs and hub genes such as DLGAP5 from independent datasets in the current study will provide clues to elucidate the molecular mechanisms involved in development and progression of ESCC.

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A second eukaryotic group with mitochondrion-encoded tmRNA: in silico identification and experimental confirmation.

Publications

A second eukaryotic group with mitochondrion-encoded tmRNA: in silico identification and experimental confirmation.

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