Project description:In bacteria and archaea, CRISPR loci confer adaptive, sequence-based immunity against viruses and plasmids. CRISPR interference is specified by CRISPR RNAs (crRNAs) that are transcribed and processed from CRISPR spacers and repeats. Pre-crRNA processing is essential for CRISPR interference in all systems studied thus far. Here we examine crRNA biogenesis and CRISPR interference in naturally competent Neisseria spp., including the human pathogen N. meningitidis. Our studies reveal a unique crRNA maturation pathway in which crRNA transcription is driven by promoters that are embedded within each repeat, yielding crRNA 5’ ends are not formed by processing. Although crRNA 3’ end formation occurs through RNase III cleavage of a pre-crRNA/tracrRNA duplex, as in other Type II CRISPR systems, this processing event is dispensable for interference. The meningococcal pathway is the most streamlined CRISPR/cas system characterized to date. Endogenous CRISPR spacers frequently target genomic sequences of other Neisseria strains and so limit natural transformation, which is the primary source of genetic variation that contributes to immune evasion, antibiotic resistance, and virulence in N. meningitidis. dRNA-seq approach for RNA samples from cultures of N. lactamica 020-06, harvested at mid-log. Two cDNA libraries from total RNA were prepared to distinguish between transcripts with either primary orprocessed 5’ ends: one library is generated from untreated RNA, whereas the other is treated with terminator exonuclease (TEX),
Project description:We perform polyA independent deep sequencing of chromatin associated primary transcripts across three different cell lines to obtain a global view on in vivo microRNA processing. We use these data to define a MicroProcessing Index (MPI), to quantify the cleavage efficiency of the Microprocessor complex. Hallmarks of efficient Drosha-mediated processing are confirmed by means of deep sequencing of chromatin-associated transcripts upon Drosha knockdown. Our results suggest that both sequence features and thermodynamic properties, e.g. secondary structure of the regions flanking the pre-miRNA hairpins are determinants for efficient processing. Our data furthermore enables us to observe endogenous microprocessor cleavage sites at nucleotide resolution. This analysis reveals the presence of non-canonical processing events occurring one helical turn distal of most efficiently cleaved miRNA precursors. We performed polyA independent deep sequencing of the chromatin-isolated RNA fraction for 5 samples: 2 replicates in HeLa cells, 1 Drosha knock down in HeLa cells, 1 sample for A549 cells and 1 sample for HEK293 cells. We also performed deep sequencing of the small RNA fraction in the same cell lines.
Project description:In bacteria and archaea, CRISPR loci confer adaptive, sequence-based immunity against viruses and plasmids. CRISPR interference is specified by CRISPR RNAs (crRNAs) that are transcribed and processed from CRISPR spacers and repeats. Pre-crRNA processing is essential for CRISPR interference in all systems studied thus far. Here we examine crRNA biogenesis and CRISPR interference in naturally competent Neisseria spp., including the human pathogen N. meningitidis. Our studies reveal a unique crRNA maturation pathway in which crRNA transcription is driven by promoters that are embedded within each repeat, yielding crRNA 5’ ends are not formed by processing. Although crRNA 3’ end formation occurs through RNase III cleavage of a pre-crRNA/tracrRNA duplex, as in other Type II CRISPR systems, this processing event is dispensable for interference. The meningococcal pathway is the most streamlined CRISPR/cas system characterized to date. Endogenous CRISPR spacers frequently target genomic sequences of other Neisseria strains and so limit natural transformation, which is the primary source of genetic variation that contributes to immune evasion, antibiotic resistance, and virulence in N. meningitidis.
Project description:The CRISPR-Cas system represents an RNA-based adaptive immune response system in prokaryotes. CRISPRs (Clustered Regularly Interspaced Short Palindromic Repeats) consist of arrays of short repeat sequences interspaced by non-repetitive short spacers, some of which show sequence similarity to foreign phage genetic elements. Their cistronic transcripts are processed to produce the mature CRISPR RNAs (crRNAs), the elements that confer immunity by base-pairing with exogenous nucleic acids. We characterized the expression and processing patterns of Thermus thermophilus HB8 CRISPRs using differential deep-sequencing, which differentiates between 5’ monophosphate and 5’ non-monophosphate-containing RNAs, and/or between 3’ hydroxyl and 3’ non-hydroxyl-containing RNAs. The genome of T. thermophilus HB8 encodes 11 CRISPRs, classified into three distinct repeat sequence types, all of which were constitutively expressed without deliberately infecting the bacteria with phage. Analysis of the differential deep sequencing data suggested that crRNAs are generated by endonucleolytic cleavage, leaving fragments with 5’ hydroxyl and 3’ phosphate or 2’,3’-cyclic phosphate termini. The 5’ ends of all crRNAs are generated by site-specific cleavage eight nucleotides upstream of the spacer start position, however, the 3’ ends, are generated by two alternative, repeat-sequence-type-dependent mechanisms. These observations are consistent with the operation of multiple crRNA processing systems within a bacterial strain.
Project description:To determine what effect the collateral activity of RfxCas13d has on HEK293T cells upon targeting overexpressed NeuN. The plasmids encoding RfxCas13d, NeuN and NT/targeting crRNA into HEK293T cells. After 24 hours of transfection, cells were collected and extracted for total RNA. Then, we performed RNA-seq to compare the differentially expressed genes between cells transfected with targeting crRNAs and non-targeting crRNA.
Project description:To determine whether target genes were specifically knocked down by RfxCas13d in N2a cells, we performed RNA-seq to compare the differentially expressed genes between cells transfected with targeting crRNAs and non-targeting crRNA.
Project description:Generating and analyzing overlapping peptides through multienzymatic digestion is an efficient procedure for de novo protein using from bottom-up mass spectrometry (MS). Despite improved instrumentation and software, de novo MS data analysis remains challenging. In recent years, deep learning models have represented a performance breakthrough. Incorporating that technology into de novo protein sequencing workflows require machine-learning models capable of handling highly diverse MS data. In this study, we analyzed the requirements for assembling such generalizable deep learning models by systematically varying the composition and size of the training set. We assessed the generated models' performances using two test sets composed of peptides originating from the multienzyme digestion of samples from various species. The peptide recall values on the test sets showed that the deep learning models generated from a collection of highly N- and C-termini diverse peptides generalized 76% more over the termini-restricted ones. Moreover, expanding the training set's size by adding peptides from the multienzymatic digestion with five proteases of several species samples led to a 2-3 fold generalizability gain. Furthermore, we tested the applicability of these multienzyme deep learning (MEM) models by fully de novo sequencing the heavy and light monomeric chains of five commercial antibodies (mAbs). MEMs extracted over 10000 matching and overlapped peptides across six different proteases mAb samples, achieving a 100% sequence coverage for 8 of the ten polypeptide chains. We foretell that the MEMs' proven improvements to de novo analysis will positively impact several applications, such as analyzing samples of high complexity, unknown nature, or the peptidomics field.