Project description:Poly(A) tails enhance the stability and translation of most eukaryotic messenger RNAs, but difficulties in globally measuring poly(A)-tail lengths have impeded greater understanding of poly(A)-tail function. Here we describe poly(A)-tail length profiling by sequencing (PAL-seq) and apply it to measure tail lengths of millions of individual RNAs isolated from yeasts, cell lines, Arabidopsis thaliana leaves, mouse liver, and zebrafish and frog embryos. Poly(A)-tail lengths were conserved between orthologous mRNAs, with mRNAs encoding ribosomal proteins and other 'housekeeping' proteins tending to have shorter tails. As expected, tail lengths were coupled to translational efficiencies in early zebrafish and frog embryos. However, this strong coupling diminished at gastrulation and was absent in non-embryonic samples, indicating a rapid developmental switch in the nature of translational control. This switch complements an earlier switch to zygotic transcriptional control and explains why the predominant effect of microRNA mediated deadenylation concurrently shifts from translational repression to mRNA destabilization.
Project description:Poly(A) tails enhance the stability and translation of most eukaryotic messenger RNAs, but difficulties in globally measuring poly(A)-tail lengths have impeded greater understanding of poly(A)-tail function. Here we describe poly(A)-tail length profiling by sequencing (PAL-seq) and apply it to measure tail lengths of millions of individual RNAs isolated from yeasts, cell lines, Arabidopsis thaliana leaves, mouse liver, and zebrafish and frog embryos. Poly(A)-tail lengths were conserved between orthologous mRNAs, with mRNAs encoding ribosomal proteins and other 'housekeeping' proteins tending to have shorter tails. As expected, tail lengths were coupled to translational efficiencies in early zebrafish and frog embryos. However, this strong coupling diminished at gastrulation and was absent in non-embryonic samples, indicating a rapid developmental switch in the nature of translational control. This switch complements an earlier switch to zygotic transcriptional control and explains why the predominant effect of microRNA mediated deadenylation concurrently shifts from translational repression to mRNA destabilization. 64 samples from a variety of species
Project description:We report systematical profiling of translation efficiency and mRNA stability dependent on the dynamics of poly(A)-tail length in stress conditions of human cells. In this study, we developed a new feasible method measuring poly(A)-tail length called TED-seq and applied it to investigate the change of mRNA's poly(A)-tail lengths in ER stress pharmacologically induced by thapsigargin (THAP). Combined with other global RNA analyses such as RNA-seq, Ribo-seq and PRO-seq, we observed that ER stress induced lenthening poly(A)-tail length, in particular of ER-stress-regulators, upon ER stress. More specifically, these mRNAs are translationally de-repressed and more stabilized based on increase in poly(A)-tail length. We also identified that insoluble fractions which include stress-induced RNA-granules have overall shorter length of poly(A) tail. Taken together, our data suggest that poly(A)-tail lengths are dynamically regulated and influence both translation efficiency and mRNA stability in ER stress.
Project description:Polyadenylation at the 3’ end of eukaryotic messenger RNAs enhances mRNA stability and translational efficiency. Global analysis for poly(A) tail lengths may shed lights on various aspects of gene regulation studies. Two NGS-based methods have been introduced for genome-wide poly(A) profiling, and they have shown human poly(A) profiles with shorter than previously conceived tail lengths. However, both methods are technically challenging and difficult to be repeated or widely adapted. Here we present a more straightforward method for poly(A) profiling. Poly(A)-seq performed on Illumina NextSeq 500 produces single-end 300 nt reads that covers the entirety of poly(A) tails, and poly(A) lengths can be directly calculated from base call data. With Poly(A)-seq we report that the global poly(A) lengths of several human cell lines may be longer than previously reported. We also show that the size selection step during Poly(A)-seq library preparation may greatly affect the sequencing profile, and thus cautions should be taken for comparisons between samples. As a convenient tool, we hope wide applications of Poly(A)-seq helps to bring better understanding of poly(A) tail properties and functions.
Project description:Poly(A) tails are critical for mRNA stability and translation. However, recent studies have challenged this view, showing that poly(A) tail length and translation efficiency are decoupled in non-embryonic cells. Using TAIL-seq and ribosome profiling, we investigate poly(A) tail dynamics and translational control in the somatic cell cycle. We find dramatic changes in poly(A) tail lengths of cell cycle regulatory genes like CDK1, TOP2A, and FBXO5, explaining their translational repression in M phase. We also find that poly(A) tail length is coupled to translation when the poly(A) tail is <20 nucleotides. However, as most genes have >20 nucleotide poly(A) tails, their translation is regulated mainly via poly(A) tail length-independent mechanisms during the cell cycle. Specifically, we find that terminal oligopyrimidine (TOP) tract-containing transcripts escape global translational suppression in M phase and are actively translated. Our quantitative and comprehensive data provide a revised view of translational control in the somatic cell cycle.
Project description:Poly(A) tails are critical for mRNA stability and translation. However, recent studies have challenged this view, showing that poly(A) tail length and translation efficiency are decoupled in non-embryonic cells. Using TAIL-seq and ribosome profiling, we investigate poly(A) tail dynamics and translational control in the somatic cell cycle. We find dramatic changes in poly(A) tail lengths of cell cycle regulatory genes like CDK1, TOP2A, and FBXO5, explaining their translational repression in M phase. We also find that poly(A) tail length is coupled to translation when the poly(A) tail is <20 nucleotides. However, as most genes have >20 nucleotide poly(A) tails, their translation is regulated mainly via poly(A) tail length-independent mechanisms during the cell cycle. Specifically, we find that terminal oligopyrimidine (TOP) tract-containing transcripts escape global translational suppression in M phase and are actively translated. Our quantitative and comprehensive data provide a revised view of translational control in the somatic cell cycle. HeLa cells were synchronized at S or M phase, and subject to RNA-seq, ribosome profiling and TAIL-seq analysis.
Project description:During oocyte maturation and early embryonic development, poly(A)-tail lengths strongly influence mRNA translation. However, how tail lengths are controlled at different developmental stages has been unclear. Here, we performed tail-length and translational profiling of mRNA reporter libraries (each with > 10 million 3ʹ-UTR sequence variants) in frog oocytes and embryos, and fish embryos. These analyses revealed that the UUUUA motif specifies cytoplasmic polyadenylation and identified diverse context features that modulate the activity of this 5-mer. Additional sequence motifs drive stage-specific deadenylation in embryos, and UUUUA and C-rich motifs drive tail-length-independent translational repression in oocytes. A neural network model accurately predicts tail-length change during oocyte maturation in frogs, mice, and humans. Analyses of human sequence variants showed that those predicted to disrupt tail-length control have been under negative selection, implying that our insights into control of poly(A)-tail length and translation have implications for human health and fertility.
Project description:This project aims to leverage Oxford Nanopore Technologies (ONT) long-read RNA sequencing to achieve a comprehensive analysis of the human pancreatic cancer transcriptome. Traditional short-read sequencing methods often struggle with accurately reconstructing full-length transcripts and discerning complex splicing events due to their limited read lengths. In contrast, ONT's long-read sequencing can generate reads that span entire RNA molecules, facilitating precise identification of transcript isoforms, alternative splicing patterns, and poly(A) tail length. By applying this technology, we seek to enhance the annotation of the pancreatic cancer transcriptome, uncover novel transcripts, and gain deeper insights into gene expression dynamics. The findings from this study have the potential to advance our understanding of gene regulation and contribute to the development of novel therapeutic strategies.
Project description:While numerous studies have described the transcriptomes of EVs in different cellular contexts, these efforts have typically relied on sequencing methods requiring RNA fragmentation, which limits interpretations on the integrity and isoform diversity of EV-encapsulated RNA populations. Furthermore, it has been assumed that mRNA signatures in EVs are likely to be fragmentation products of the cellular mRNA material, and little is known about the extent to which full-length mRNAs are present within EVs. Using Oxford nanopore long-read RNA sequencing, we sought to characterize the full-length polyadenylated (poly-A) transcriptome of EVs released by human chronic myelogenous leukemia K562 cells. We detected 441 and 280 RNAs that were respectively enriched or depleted in EVs. EV-enriched poly-A transcripts consist of a variety of biotypes, including mRNAs, long non-coding RNAs, and pseudogenes. Our analysis revealed that 12.72% of all reads present in EVs corresponded to known full-length transcripts, 65.34% of which were mRNAs. We also observed that for many well-represented coding and non-coding genes, diverse full-length transcript isoforms were present in EV specimens, and these isoforms were reflective-of but often in different ratio compared to cellular samples. Here we report a full-length transcriptome from human EVs, as determined by long-read nanopore sequencing.
Project description:We optimized a protocol to enrich, digest and add poly(A) tail to the circular RNAs in order to make them compatible with the Oxfor Nanopore Technology for full-length sequencing