Project description:For a typical RNA polymerase (pol) II transcribed budding yeast gene, the 5' -end is characterized by a nucleosome-free region (NFR) immediate upstream of the transcription start site (TSS), flanked by two well-positioned nucleosomes (-1 and +1) containing H2A.Z. A similar arrangement of nucleosomes containing H2A.Z is found on the genes transcribed by pol III, which reside in the NFR actively maintained by the chromatin remodeling complexes. We did genome-wide MNase-seq and ChIP-seq experiments to study the nucleosome arrangement near pol III transcribed genes. We also measured the levels of different tRNAs in the tRNA pool of the wild type and Spt16 mutant (*spt16-197*) cells using tRNA-HySeq method. Although, it is difficult to measure the primary transcripts of tRNA due to their quick processing and the sequence degeneracy of the tRNA isogenes; a comparison of the wild type and Spt16 mutant showed both increase or decrease of tRNA transcripts. The result suggest that Spt16 may not be necessary for the transcription per se of tRNA genes.
Project description:A tet-off strain of Saccharomyces cerevisiae was constructed in which the GLN4 glutamine tRNA synthetase gene was placed under control of a doxycycline-regulated promoter. The transcriptional responses to Gln4p tRNA synthetase depletion were assessed by growth of the strain in the presence, or absence, of doxycycline (1 µg/ml). A control, wild-type strain was similarly treated with doxycycline or left untreated as a reference. Each strain/condition RNA isolation was performed using triplicate independent biological samples A, B and C.
Project description:Different subsets of the tRNA pool in human are expressed in different cellular conditions. The “proliferation-tRNAs” are induced upon normal and cancerous cell division, while the “differentiation tRNAs” are active in non-dividing, differentiated cells. Here we examine the essentiality of the various tRNAs upon cellular growth and arrest. We established a CRISPR-based editing procedure with sgRNAs that each target a tRNA family. We measured tRNA essentiality for cellular growth and found that most proliferation tRNAs are essential compared to differentiation tRNAs in rapidly growing cell lines. Yet in more slowly dividing lines, the differentiation tRNAs were more essential. In addition, we measured the essentiality of each tRNA family upon response to cell cycle arresting signals. Here we detected a more complex behavior with both proliferation-tRNAs and differentiation-tRNAs showing various levels of essentiality. These results provide the so-far most comprehensive functional characterization of human tRNAs with intricate roles in various cellular states.
Project description:Transfer RNAs (tRNAs) maintain translational fidelity through strict charging by their cognate aminoacyl-tRNA synthetase and codon:anticodon base pairing with the mRNA at the ribosome. Mistranslation occurs when an amino acid not specified by the genetic code is incorporated into a protein. Since alanyl-tRNA synthetase uniquely recognizes a G3:U70 base pair in alanine tRNAs and the anticodon plays no role in charging, alanine tRNA variants with anticodon mutations have the potential to mistranslate alanine. Our goal was to quantify mis-incorporation of alanine into proteins in Saccharomyces cerevisiae strains expressing one of 57 different alanine tRNA anticodon variants. Using mass spectrometry, we observed mistranslation for 45 of the variants when expressed on single-copy plasmids.
Project description:Different subsets of the tRNA pool in human are expressed in different cellular conditions. The “proliferation-tRNAs” are induced upon normal and cancerous cell division, while the “differentiation tRNAs” are active in non-dividing, differentiated cells. Here we examine the essentiality of the various tRNAs upon cellular growth and arrest. We established a CRISPR-based editing procedure with sgRNAs that each target a tRNA family. We measured tRNA essentiality for cellular growth and found that most proliferation tRNAs are essential compared to differentiation tRNAs in rapidly growing cell lines. Yet in more slowly dividing lines, the differentiation tRNAs were more essential. In addition, we measured the essentiality of each tRNA family upon response to cell cycle arresting signals. Here we detected a more complex behavior with both proliferation-tRNAs and differentiation-tRNAs showing various levels of essentiality. These results provide the so-far most comprehensive functional characterization of human tRNAs with intricate roles in various cellular states.
Project description:Different subsets of the tRNA pool in human are expressed in different cellular conditions. The “proliferation-tRNAs” are induced upon normal and cancerous cell division, while the “differentiation tRNAs” are active in non-dividing, differentiated cells. Here we examine the essentiality of the various tRNAs upon cellular growth and arrest. We established a CRISPR-based editing procedure with sgRNAs that each target a tRNA family. We measured tRNA essentiality for cellular growth and found that most proliferation tRNAs are essential compared to differentiation tRNAs in rapidly growing cell lines. Yet in more slowly dividing lines, the differentiation tRNAs were more essential. In addition, we measured the essentiality of each tRNA family upon response to cell cycle arresting signals. Here we detected a more complex behavior with both proliferation-tRNAs and differentiation-tRNAs showing various levels of essentiality. These results provide the so-far most comprehensive functional characterization of human tRNAs with intricate roles in various cellular states.
Project description:Transfer RNAs (tRNA) are quintessential in deciphering the genetic code; disseminating nucleic acid triplets into correct amino acid identity. While this decoding function is clear, an emerging theme is that tRNA abundance and functionality can powerfully impact protein production rate, folding, activity, and messenger RNA stability. Importantly, however, the expression pattern of tRNAs (in even simple systems) is obliquely known. Limited analysis suggests tRNA levels change during proliferation, differentiation, cancer, and neurodegeneration; possibly mediating changes in translation efficiency and mRNA stability. A major limitation for the field has been the ability to subject tRNA pools to high-throughput analysis as they are highly structured, modified, and of high sequence similarity. Here we present Quantitative Mature tRNA sequencing (QuantM-tRNA seq), an easily implemented high-throughput technique to monitor tRNA abundance and sequence variants (possibly due to RNA modifications). With QuantM-tRNA seq we provide a comprehensive analysis of the tRNA transcriptome from distinct mammalian tissues. We observe dramatic distinctions in isodecoder expression and likely RNA modifications between unique tissues with a particularly strong signature within the central nervous system. Remarkably, despite dramatic changes in tRNA isodecoder gene expression, the overall anticodon pool of each tRNA family is similar. These findings suggest that anticodon pools are buffered via an unknown mechanism to achieve uniform decoding throughout the body.