Project description:Chemical probing has the power to provide insight into RNA conformation in vivo and in vitro, but interpreting the results depends on methods to detect the chemically modified nucleotides. Traditionally, the presence of modified bases was inferred from their ability to halt reverse transcriptase during primer extension and the locations of termination sites observed by electrophoresis or sequencing. More recently, modification-induced mutations have been used as a readout for chemical probing data. Given variable propensity for mismatch incorporation and read-through with different reverse transcriptases, we examined how termination and mutation events compare to each other in the same chemical probing experiments. We found that mutations and terminations induced by dimethyl sulfate probing are both specific for methylated bases, but these two measures have surprisingly little correlation and represent largely non-overlapping indicators of chemical modification data. We also show that specific biases for modified bases depend partly on local sequence context, and that different reverse transcriptases show different biases toward reading a modification as a stop or a mutation. These results support approaches that incorporate analysis of both termination and mutation events into RNA probing experiments.
Project description:Structure probing experiments were performed on in vitro transcripts and E. coli and human cell cultures under natively extracted (cell-free) and in-cell conditions to benchmark the performance of the newly introduced PAIR-MaP correlated chemical probing strategy for detecting RNA duplexes. Multiple-hit dimethyl sulfate (DMS) probing was done using new buffer conditions that facilitate DMS modification of all four nucleotides.
Project description:We identified a SNP rs242561, located within a regulatory region of the MAPT gene (encoding microtubule-associated protein Tau). It was consistently occupied by NRF2/sMAF in multiple ChIP-seq experiments, and its strong-binding allele increased transactivation, and accorded higher mRNA levels in cell lines and human brain. To confirm the allele-specific binding, we conducted ChIP tagmentaion sequencing experiment in human lymphoblastoid cell line GM12763 which is heterozygous for rs242561. NRF2 ChIP DNA was isolated from GM12763 cells treated with Sulforaphane (SFN) in triplicates. The region containing rs242561 was amplified using primers, Fwd 5â??-AGCCTTCCCTGTCCTTGATT-3â??, Rev 5â??-GGACCGAGCTTCCAGTCTAA-3â??, and tagmentated using Tn5-based transposition for library construction. Libraries were sequenced on Illumina MiSeq. NRF2 ChIP tagmentation sequencing of a 241bp intron region in MAPT gene using GM12763 treated with sulforaphane
Project description:The nuclear envelope serves as important mRNA surveillance system. In yeast and human, several control systems act in parallel to prevent nuclear export of unprocessed mRNAs. Trypanosomes lack homologues to most of the involved proteins and their nuclear mRNA metabolism is non-conventional exemplified by polycistronic transcription and mRNA processing by trans-splicing. We here visualised nuclear export in trypanosomes by probing large, endogenous mRNA by intramolecular multi-colour single molecule FISH (smFISH). In addition, unspliced mRNAs were visualised by co-probing two adjacent introns or intergenic regions. We found that the initation of nuclear export requires neither the completion of transcription nor trans-splicing. Nevertheless, the inhibition of trans-splicing blocked cytoplasmic transport of the of unspliced mRNAs and only a small fraction reached the nucleus-distant cytoplasm. Most of the unspliced transcripts remained at the nuclear periphery, within transport and in nuclear periphery granules (NPGs) localised at the cytoplasmic site of nuclear pores that resemble stress granules in composition. Our work shows that, in striking contrast to other eukaryotes, trypanosomes can start nuclear export while the mRNA is still transcribed, but unspliced transcripts remain ‘stuck’ in nuclear pores, probably awaiting processing or decay. Our data indicate that trypanosomes regulate the completion of nuclear export rather than the start.
Project description:Tau is encoded by MAPT and abnormal aggregates of tau are a hallmark of a group of neurodegenerative diseases called tauopathies. MAPT is lowly expressed in neural progenitor cells (NPCs), but it is more highly expressed in oligodendrocytes, astrocytes, and neurons that derive from NPCs. This expression switch at differentiation suggests that MAPT expression is controlled by transcription factors and cis-regulatory elements specific to these differentiated cell types, including neurons.
Project description:Tau is encoded by MAPT and abnormal aggregates of tau are a hallmark of a group of neurodegenerative diseases called tauopathies. MAPT is lowly expressed in neural progenitor cells (NPCs), but it is more highly expressed in oligodendrocytes, astrocytes, and neurons that derive from NPCs. This expression switch at differentiation suggests that MAPT expression is controlled by transcription factors and cis-regulatory elements specific to these differentiated cell types, including neurons.
Project description:Deciphering the conformations of RNAs in their cellular environment allows identification of RNA elements with potentially functional roles within biological contexts. Insight into the conformation of RNA in cells has been achieved using chemical probes that were developed to react specifically with flexible RNA nucleotides, or the Watson-Crick face of single-stranded nucleotides. The most widely used probes are either selective SHAPE (2'-hydroxyl acylation and primer extension) reagents that probe nucleotide flexibility, or dimethyl sulfate (DMS), which probes the base-pairing at adenine and cytosine but is unable to interrogate guanine or uracil. The constitutively charged carbodiimide N-cyclohexyl-N'-(2-morpholinoethyl)carbodiimide metho-p-toluenesulfonate (CMC) is widely used for probing G and U nucleotides, but has not been established for probing RNA in cells. Here, we report the use of a smaller and conditionally charged reagent, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), as a chemical probe of RNA conformation, and the first reagent validated for structure probing of unpaired G and U nucleotides in intact cells. We showed that EDC demonstrates similar reactivity to CMC when probing transcripts in vitro. We found that EDC specifically reacted with accessible nucleotides in the 7SK noncoding RNA in intact cells. We probed structured regions within the Xist lncRNA with EDC and integrated these data with DMS probing data. Together, EDC and DMS allowed us to refine predicted structure models for the 3’ extension of repeat C within Xist. These results highlight how complementing DMS probing experiments with EDC allows the analysis of Watson-Crick base-pairing at all four nucleotides of RNAs in their cellular context.
Project description:The aim of this experiment was to assess the on- and off-target effects of MAPT-AS1 expression, and whether mutations/deletions to MAPT-AS1 alter these effects. SHSY5Y cells stably expressing variants of MAPT-AS1 were analyzed by Riboseq and Quantseq.