Project description:Transfer RNA (tRNA) plays a central role in translation. Simultaneously synthesizing the minimal yet sufficient number of tRNA species (at least 21) in vitro poses a challenge to constructing a self-reproducible artificial cell. In this study, we developed a simplified processing method that enables the simultaneous expression of all 21 tRNAs in a reconstituted transcription/translation system (PURE system). By combining direct tRNA linkage and HDVR attachment methods, termed the tRNA array method, we achieved simultaneous expression of all 21 tRNAs from a single polycistronic DNA template in the PURE system.
This method allows for the easy customization of the genetic code by introducing additional tRNAs. To demonstrate genetic code reassignment, we replaced five Leu residues (CUU) in Nanoluc with ACG, which is assigned to Thr in the native codon table. To confirm amino acid reassignment, we performed LC-MS/MS analysis of translated Nanoluc proteins. The results confirmed the incorporation of threonine at the reassigned ACG codon in the presence of tRNA^Thr_CGU, and leucine incorporation when using tRNA^Leu_CGU.
Project description:Small noncoding RNAs (sncRNAs) are implicated in age-associated pathologies, including sarcopenia and insulin resistance (IR). This study aimed to characterise the wider circulating sncRNA transcriptome of older individuals and associations with sarcopenia and IR. Total RNA was used for sncRNA expression including miRNAs, transfer RNAs (tRNAs), tRNA-associated fragments (tRFs) and piwi-interacting RNAs (piRNAs) was measured in serum from 21 healthy and 21 sarcopenic women matched for age (mean 78.9 years) and HOMA2-IR from the Hertfordshire Sarcopenia Study. Associations with age, sarcopenia and HOMA2-IR were examined, and predicted gene targets and biological pathways characterised.
Project description:Despite its biological importance, transfer RNA (tRNA) could not be adequately sequenced due to the abundant presence of post-transcriptional modifications and extensive structure that interfere with cDNA synthesis and adapter ligation. We achieve efficient and quantitative tRNA sequencing by removing base methylations using engineered demethylases and using a highly processive thermo-stable reverse transcriptase without the need for adapter ligation (DMTRT-tRNA-seq). Our method should be applicable for biological investigations of tRNA in all organisms. Development of tRNA-Seq method
Project description:Small RNAs include tRNA, snRNA, micro-RNA, tRNA fragments and others that constitute >90% of RNA copy numbers in a human cell and perform many essential functions. Popular small RNA-seq strategies limit the insights into coordinated small RNA response to cellular stress. Small RNA-seq also lacks multiplexing capabilities. Here, we report a multiplex small RNA-seq library preparation method (MSR-seq) to investigate cellular small RNA and mRNA response to heat shock, hydrogen peroxide, and arsenite stress. Comparing stress-induced changes of total cellular RNA and polysome-associated RNA, we identify a coordinated tRNA response that involves polysome-specific tRNA abundance and synergistic N3-methylcytosine (m3C) tRNA modification. Combining tRNA and mRNA response to stress we reveal a new mechanism of stress-induced down-regulation in translational elongation. We also find that native tRNA molecules lacking several modifications are biased reservoirs for the biogenesis of tRNA fragments. Our results demonstrate the importance of simultaneous investigation of small RNAs and their modifications in response to varying biological conditions.
Project description:Specific environmental insults cause the limited fragmentation of transfer RNAs (tRNAs) into tRNA-derived small RNAs (tsRNAs), which have been implicated in a wide range of biological processes. tRNA fragmentation results from endonucleolytic activities targeting single-stranded tRNA regions. However, how a tRNA with a single hydrolyzed phosphodiester bond in the anticodon loop (‘nicked’ tRNA) gives rise to distinct tsRNAs remains poorly understood. After identifying RNA helicases that were able to unwind ‘nicked’ tRNAs in vitro, the specificity of one of those enzymes, DDX3X, was determined by RNA helicase assays on tRNAs, which had been subjected to recombinant Angiogenin. Both in vivo ‘nicked’ tRNAs, DDX3X-unwound ‘nicked’ tRNAs as well as heat-denatured ‘nicked’ tRNAs were subjected to small RNA sequencing.
Project description:The participation of transfer RNAs (tRNAs) in fundamental aspects of biology and disease necessitates an accurate, experimentally confirmed annotation of tRNA genes, and curation of precursor and mature tRNA sequences. This has been challenging, mainly because RNA secondary structure and nucleotide modifications, together with tRNA gene multiplicity, complicate sequencing and sequencing read mapping efforts. To address these issues, we developed hydro-tRNAseq, a method based on partial alkaline RNA hydrolysis that generates fragments amenable for sequencing. To identify transcribed tRNA genes, we further complemented this approach with Photoactivatable Crosslinking and Immunoprecipitation (PAR-CLIP) of SSB/La, a conserved protein involved in pre-tRNA processing. Our results show that approximately half of all predicted tRNA genes are transcribed in human cells. We also report predominant nucleotide modification sites, their order of introduction, and identify tRNA leader, trailer and intron sequences. By using complementary sequencing-based methodologies, we present a human tRNA atlas, and determine expression levels of mature and processing intermediates of tRNAs in human cells.
Project description:Autosomal-recessive loss of the NSUN2 gene has been recently identified as a causative link to intellectual disability disorders in humans. NSun2 is an RNA methyltransferase modifying cytosine-5 in transfer RNAs (tRNA). Whether NSun2 methylates additional RNA species is currently debated. Here, we adapted the individual-nucleotide resolution UV cross-linking and immunoprecipitation method (iCLIP) to identify NSun2-mediated methylation in RNA transcriptome. We confirm site-specific methylation in tRNA and identify messenger and non-coding RNAs as potential methylation targets for NSun2. Using RNA bisulfite sequencing we establish Vault non-coding RNAs as novel substrates for NSun2 and identified six cytosine-5 methylated sites. Furthermore, we show that loss of cytosine-5 methylation in Vault RNAs causes aberrant processing into argonaute-associating small RNA fragments (svRNA). Thus, impaired Vault non-coding RNA processing may be an important contributor to the etiology of NSUN2-deficieny human disorders. mRNA-seq in Embryonic kidney (HEK293) cells transfected with siRNA against Nsun2 vs control
Project description:Autosomal-recessive loss of the NSUN2 gene has been recently identified as a causative link to intellectual disability disorders in humans. NSun2 is an RNA methyltransferase modifying cytosine-5 in transfer RNAs (tRNA). Whether NSun2 methylates additional RNA species is currently debated. Here, we adapted the individual-nucleotide resolution UV cross-linking and immunoprecipitation method (iCLIP) to identify NSun2-mediated methylation in RNA transcriptome. We confirm site-specific methylation in tRNA and identify messenger and non-coding RNAs as potential methylation targets for NSun2. Using RNA bisulfite sequencing we establish Vault non-coding RNAs as novel substrates for NSun2 and identified six cytosine-5 methylated sites. Furthermore, we show that loss of cytosine-5 methylation in Vault RNAs causes aberrant processing into argonaute-associating small RNA fragments (svRNA). Thus, impaired Vault non-coding RNA processing may be an important contributor to the etiology of NSUN2-deficieny human disorders. Identification of Nsun2 targets by miCLIP in Embryonic kidney (HEK293) cells
Project description:Progesterone receptors (PR) can regulate transcription by RNA Polymerase III (Pol III), which transcribes small non-coding RNAs, including all transfer RNAs (tRNAs). This and previous work demonstrated that PR associates with the Pol III complex at tRNA genes and that progestins downregulate tRNA transcripts in breast tumor models.
Project description:Autosomal-recessive loss of the NSUN2 gene has been recently identified as a causative link to intellectual disability disorders in humans. NSun2 is an RNA methyltransferase modifying cytosine-5 in transfer RNAs (tRNA). Whether NSun2 methylates additional RNA species is currently debated. Here, we adapted the individual-nucleotide resolution UV cross-linking and immunoprecipitation method (iCLIP) to identify NSun2-mediated methylation in RNA transcriptome. We confirm site-specific methylation in tRNA and identify messenger and non-coding RNAs as potential methylation targets for NSun2. Using RNA bisulfite sequencing we establish Vault non-coding RNAs as novel substrates for NSun2 and identified six cytosine-5 methylated sites. Furthermore, we show that loss of cytosine-5 methylation in Vault RNAs causes aberrant processing into argonaute-associating small RNA fragments (svRNA). Thus, impaired Vault non-coding RNA processing may be an important contributor to the etiology of NSUN2-deficieny human disorders.