Project description:microRNAs are frequently modified by addition of untemplated nucleotides to the 3' end, but the role of this tailing is often unclear. Here we characterize the prevalence and functional consequences of microRNA tailing in vivo, using Caenorhabditis elegans. MicroRNA tailing in C. elegans consists mostly of mono-uridylation of mature microRNA species, with rarer mono-adenylation which is likely added to microRNA precursors. Through a targeted RNAi screen, we discover that the TUT4/TUT7 gene family member CID-1/CDE-1/PUP-1 is required for uridylation, whereas the GLD2 gene family member F31C3.2-here named GLD-2-related 2 (GLDR-2)-is required for adenylation. Thus, the TUT4/TUT7 and GLD2 gene families have broadly conserved roles in miRNA modification. We specifically examine the role of tailing in microRNA turnover. We determine half-lives of microRNAs after acute inactivation of microRNA biogenesis, revealing that half-lives are generally long (median = 20.7 h), as observed in other systems. Although we observe that the proportion of tailed species increases over time after biogenesis, disrupting tailing does not alter microRNA decay. Thus, tailing is not a global regulator of decay in C. elegans. Nonetheless, by identifying the responsible enzymes, this study lays the groundwork to explore whether tailing plays more specialized context- or miRNA-specific regulatory roles.
Project description:We cultured htertHME, HME2, PCS600010, and MCF10A cells in decellularized ECM scaffolds generated by BJ fibroblasts or on an uncoated, plastic cell culture dish (Unc) to analyze the potential effects of ECM signalling breast cancer development. Total RNA was extracted from cells using TRIzol (Invitrogen) and purified using Direct-zol RNA mini kit (Zymo Research) with DNase I treatment. After RNA purification, samples were confirmed to have a RIN value > 9.0 when measured on an Agilent Bioanalyzer. Libraries for RNA-Seq were prepared with KAPA Stranded RNA-Seq Kit. The workflow consisted of mRNA enrichment, cDNA generation, end repair to generate blunt ends, A-tailing, adaptor ligation and 12 cycles of PCR amplification. Unique adaptors were used for each sample in order to multiplex samples into several lanes. Sequencing was performed on Illumina Hiseq 3000/4000 with a 150bp pair-end run. A data quality check was done on Illumina SAV. Demultiplexing was performed with Illumina Bcl2fastq2 v 2.17 program.
Project description:In Trypanosoma brucei, most mitochondrial mRNAs undergo U-insertion/deletion editing, and 3′ adenylation and uridylation. The internal sequence changes and terminal extensions are coordinated: Pre-editing addition of the short (A) tail protects the edited transcript against 3′-5′ degradation, while post-editing A/U-tailing renders mRNA competent for ribosome recruitment. Participation of a poly(A) binding protein (PABP) in coupling of editing and 3′ modification processes has been inferred, but its identity and mechanism of action remained elusive. We report identification of KPAF4, a pentatricopeptide repeat-containing PABP which sequesters the A-tail and impedes exonucleolytic degradation. Conversely, KPAF4 inhibits uridylation of A-tailed transcripts and, therefore, premature A/U-tailing of partially-edited mRNAs. This quality check point prevents translation of incompletely edited mRNAs. Our findings also implicate the RNA editing substrate binding complex (RESC) in mediating the interaction between the 5′-end bound pyrophosphohydrolase MERS1 and 3′-end associated KPAF4 to enable mRNA circularization. This event is critical for transcript stability during the editing process.
Project description:Cervical cancer is a global public health subject as it affects women in the reproductive ages, and accounts for the second largest burden among cancer patients worldwide with an unforgiving 50% mortality rate. Poor awareness and access to effective diagnosis have led to this enormous disease burden, calling for point-of-care, minimally invasive diagnosis methods. Here, an end-to-end quantitative approach for a new kind of diagnosis has been developed, comprising identification of optimal biomarkers, design of the sensor, and simulation of the diagnostic circuit. Using miRNA expression data in the public domain, we identified circulating miRNA biomarkers specific to cervical cancer using multi-tier screening. Synthetic riboregulators called toehold switches specific for the biomarker panel were then designed. To predict the dynamic range of toehold switches for use in genetic circuits as biosensors, we developed a generic grammar of these switches, and built a multivariate linear regression model using thermodynamic features derived from RNA secondary structure and interaction. The model yielded predictions of toehold efficacy with an adjusted R2 = 0.59. Reaction kinetics modelling was performed to predict the sensitivity of the second-generation toehold switches to the miRNA biomarkers. Simulations showed a linear response between 10nM and 100nM before saturation. Our study demonstrates an end-to-end workflow for the efficient design of genetic circuits geared towards the effective detection of unique genomic signatures that would be increasingly important in today’s world. The approach has the potential to direct experimental efforts and minimise costs. All resources are provided open-source (https://github.com/igem2019) under GNU GPLv3 licence.
Project description:RNA tails play integral roles in the control of mRNA translation and decay. Guanylation of poly(A) tail was discovered recently, yet the enzymology and function remain obscure. Here we identify TUT3 (PAPD5) and TUT5 (PAPD7) (TUT3/5) as the enzymes responsible for mRNA guanylation. Purified TUT3/5 predominantly incorporate GTPs to generate a mixed poly(A) tail with intermittent non-adenosine residues. A single guanosine is sufficient to impede the deadenylation complex (CCR4-NOT) which trims the tail and exposes guanosine at the 3′ end. Consistently, the depletion of TUT3/5 leads to a decrease in mRNA half-life and abundance in cells. Thus, TUT3/5 produce a mixed tail which shields the mRNA from rapid deadenylation. Our study unveils the role of mixed tailing, and expands the complexity of post-transcriptional gene regulation.
Project description:RNA tails play integral roles in the control of mRNA translation and decay. Guanylation of poly(A) tail was discovered recently, yet the enzymology and function remain obscure. Here we identify TUT3 (PAPD5) and TUT5 (PAPD7) (TUT3/5) as the enzymes responsible for mRNA guanylation. Purified TUT3/5 predominantly incorporate GTPs to generate a mixed poly(A) tail with intermittent non-adenosine residues. A single guanosine is sufficient to impede the deadenylation complex (CCR4-NOT) which trims the tail and exposes guanosine at the 3′ end. Consistently, the depletion of TUT3/5 leads to a decrease in mRNA half-life and abundance in cells. Thus, TUT3/5 produce a mixed tail which shields the mRNA from rapid deadenylation. Our study unveils the role of mixed tailing, and expands the complexity of post-transcriptional gene regulation.