Project description:We combined RNA metabolic labeling and alkylation with droplet-based sequencing to detect newly synthesized mRNAs in single cells. With the classification of labeled and unlabeled precursor and mature mRNAs, we modeled and analyzed the time-dependent RNA kinetic rates associated with the cell cycle. We found both transcription and degradation rates are highly dynamic over the cell cycle and different kinetic regulation types were observed for cycling genes.
Project description:Analysis methods based on simulations and optimization have been previously developed to estimate relative translation rates from next-generation sequencing data. Translation involves molecules and chemical reactions; hence, bioinformatics methods consistent with the laws of chemistry and physics are more likely to produce accurate results. Here, we derive simple equations based on chemical kinetic principles to measure the translation-initiation rate, transcriptome-wide elongation rate, and individual codon translation rates from ribosome profiling experiments. Our methods reproduce the known rates from ribosome profiles generated from detailed simulations of translation. Applying our methods to data from S. cerevisiae and mouse embryonic stem cells we find that the extracted rates reproduce previously reported correlations with various molecular quantities. A codon can exhibit up to 26-fold variability in its translation rate depending upon its context with in a transcript. This broad distribution means that the average translation rate of a codon is not representative of the rate at which most instances of that codon are translated. We also find that mouse embryonic stem cells have a global translation speed that is almost two-fold faster than previously reported. This large variability in translation rates suggests that translational regulation might be used by cells to a greater degree than previously thought.
Project description:The mRNA m6A reader YTHDF2 is overexpressed in a broad spectrum of human acute myeloid leukemias (AML). To study the role of YTHDF2 on mRNA decay rates in leukemia, c-Kit+ cells from foetal livers of Ythdf2fl/fl; Vav-iCre (Ythdf2CKO) and Ythdf2fl/fl (Ythdf2CTL) 14.5 dpc embryos were transduced with Meis1 and Hoxa9 oncogenes and serially re-plated to generate pre-leukemic cells. Medium with 4SU was used for pre-leukemic cells labelling for 12 hours and was later replaced with 4SU-free medium (time 0). Cells were collected immediately after medium change and at 1, 3 and 9 hours for library generation. RNA from Ythdf2CKO (n=3 biological replicates) and Ythdf2CTL (n=3 biological replicates) pre-leukemic cells were used for SLAM-seq library generation.
Project description:Purpose: Slam protein and RNA co-localize in early drosophila embryos. slam RNA specifically co-immunoprecipitates with its own protein from embryonic lysate as shown by RNA-IP and QRT-PCR. The goal of this study is to survey transcriptome wide (RNA-seq) targets of slam protein and validate the data from qRT–PCR analysis. Methods: RNA-ip was performed for staged embryos (1.5 – 3 h after egg laying) Using slam antibody or GFP binder. RNA profiles in immune-predicates were generated by deep sequencing. Results: Slam RNA specifically co-predicates with slam protein as shown by both next generation sequencing and RT-QPCR. No mRNA of other genes was detected in all independent experiments or showed the averaged enrichment in the same range.
Project description:Gene expression analysis requires accurate measurements of global RNA degradation rates, earlier problematic with methods disruptive to cell physiology. Recently, metabolic RNA labeling emerged as an efficient and minimally invasive technique applied in mammalian cells. Here, we have adapted SH-Linked Alkylation for the Metabolic Sequencing of RNA (SLAM-Seq) for a global mRNA stability study in yeast using 4-thiouracil pulse-chase labeling. We assign high-confidence half-life estimates for 67.5 % of expressed ORFs, and measure a median half-life of 9.4 min. For mRNAs where half-life estimates exist in the literature, their ranking order was in good agreement with previous data, indicating that SLAM-Seq efficiently classifies stable and unstable transcripts. We then leveraged our yeast protocol to identify targets of the Nonsense-mediated decay (NMD) pathway by measuring the change in RNA half-lives; instead of steady-state RNA level changes. With SLAM-Seq, we assign 580 transcripts as putative NMD targets, based on their measured half-lives in wild-type and upf3Δ mutants. We find 225 novel targets, and observe a strong agreement with previous reports of NMD targets, 61.2 % of our candidates being identified in previous studies.This indicates that SLAM-Seq is a simpler and more economic method for global quantification of mRNA half-lives. Our adaptation for yeast yielded global quantitative measures of the NMD effect on transcript half-lives, high correlation with RNA half-lives measured previously with more technically challenging protocols, and identification of novel NMD regulated transcripts that escaped prior detection.
Project description:Histone deacetylases (HDACs) are critical in the control of gene expression and dysregulation of their activity has been implicated in a broad range of diseases including cancer, cardiovascular and neurological diseases. HDAC inhibitors (HDACi) employing different zinc chelating functionalities such as hydroxamic acids and benzamides have shown promising results in cancer therapy. While it has also been suggested that HDACi with increased isozyme-selectivity and potency may broaden their clinical utility and minimize side effects, the translation of this idea to the clinic remains to be investigated. Moreover, a detailed understanding of how HDACi with different pharmacological properties affect biological functions in vitro and in vivo is still missing. Here we show that a panel of benzamide-containing HDACi are slow tight-binding inhibitors with long residence times unlike the hydroxamate-containing HDACi SAHA and TSA. Characterization of changes in H2BK5 and H4K14 acetylation following HDACi treatment in the neuroblastoma cell line SH-SY5Y revealed that the timing and magnitude of histoneacetylation mirrored both the association and dissociation kinetic rates of the inhibitors. In contrast, cell viability and microarray gene expression analysis indicated that cell death induction and changes in transcriptional regulation do not correlate with the dissociation kinetic rates of the HDACi. Therefore, our study suggests that the evaluation of different classes of HDACi compounds using recombinant HDACs or histone acetylation is insufficient to predict their functional impact on cell activity. Control, SAHA 6hr, SAHA 24hr, SAHA 24hr (pulsed), C1 6hr, C1, 24hr, C1 24hr (pulsed)