Translation initiation at a non-AUG start codon for mouse and human NELF-B
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ABSTRACT: Negative elongation factor (NELF), a four-subunit protein complex in metazoan, plays an important role in regulating promoter-proximal pausing of RNA polymerase II (RNAPII). Genetic studies demonstrate that the B subunit of mouse NELF (NELF-B) is critical for embryonic development and homeostasis in adult tissue. We report here that both human and mouse NELF-B proteins are translated from a non-AUG codon upstream of the annotated AUG. This non-AUG codon sequence is conserved in mammalian NELF-B but not NELF-B orthologs of lower metazoan. The full-length and a truncated NELF-B that starts at the first AUG codon interact with the other three NELF subunits with comparable efficiency. Furthermore, these two forms of NELF-B have a similar impact on the transcriptomics and proliferation of mouse embryonic fibroblasts. These results strongly suggest that additional amino acid sequence upstream of the annotated AUG is dispensable for the essential function of NELF in supporting cell growth in vitro. While the majority of mouse adult tissues surveyed exclusively express the full-length NELF-B protein, mouse kidney only contains a truncated NELF-B protein with the same apparent size as the AUG-initiated version. This result raises the distinct possibility that translational initiation of mouse NELF-B is regulated in a tissue-dependent manner. triplicates for ATG-Nelf-B, triplicates for FL-Nelf-B
Project description:Negative elongation factor (NELF) is known to enforce promoter-proximal pausing of RNA polymerase II (Pol II), a pervasive phenomenon observed across multicellular genomes. However, the physiological impact of NELF on tissue homeostasis remains unclear. Here we show for the first time that whole-body conditional deletion of the B subunit of NELF (NELF-B) in adult mice results in cardiomyopathy and impaired response to cardiac stress. Tissue-specific knockout of NELF-B confirms its cell-autonomous function in cardiomyocytes. NELF directly supports transcription of those genes encoding rate-limiting enzymes in fatty acid oxidation and the tricarboxylic acid (TCA) cycle. NELF also shares extensively transcriptional target genes with peroxisome proliferator-activated receptors alpha (PPARalpha), a master regulator of energy metabolism in myocardium. Mechanistically, NELF helps stablize the transcription initation complex at the metabolism-related genes. Our findings strongly indicate that NELF is part of the PPARalpha-mediated transcription regulatory network that maintains metabolic homeostasis in cardiomyocytes. 3 Nelf-b f/f and 3 Nelf-b f/f; CreER female mice were injected with Tamoxifen at 8 wk old. Heart tissue were harvested at 20 wks old and used for RNA preparation.
Project description:Many mammalian genes are occupied by paused RNA polymerase II (pol II) at promoter-proximal regions on both sides of transcription start sites (TSSs). However, the consequences of pol II pausing on gene expression and cell biology are not fully understood. Here we report that genetic ablation of the b subunit of mouse negative elongation factor (Nelf-b), a key pol II-pausing factor, results in slower progression at multiple cell cycle stages and increased apoptosis. Consistently, a whole-genome analysis indicates that growth and cell death-related genes are highly enriched among the direct target genes of Nelf-b. In particular, Nelf-b deletion increases pol II density in the promoter-distal region of stress response genes and their overall expression levels in the absence of any external stress signals. In addition, our work also reveals a previously unappreciated role of Nelf-b role in curbing TSS-upstream transcription of many mammalian genes. We suggest that Nelf-mediated pol II pausing balances the cellular needs for growth/survival and stress response by preventing excessive basal transcription of stress-induced genes. Immortalized mouse embryonic fibroblasts derived from a Nelf-b flox/- embryo were infected with control or Cre-epxressing retrovirus. Gene expression profile of control and knockout MEF at 7 days after virus infection were compared by using Illumina's mouse whole-genome gene expression BeadChIPs. There are two replicates for both control and knockout MEF samples.
Project description:Negative elongation factor (NELF), a four-subunit protein complex in metazoan, plays an important role in regulating promoter-proximal pausing of RNA polymerase II (RNAPII). Genetic studies demonstrate that the B subunit of mouse NELF (NELF-B) is critical for embryonic development and homeostasis in adult tissue. We report here that both human and mouse NELF-B proteins are translated from a non-AUG codon upstream of the annotated AUG. This non-AUG codon sequence is conserved in mammalian NELF-B but not NELF-B orthologs of lower metazoan. The full-length and a truncated NELF-B that starts at the first AUG codon interact with the other three NELF subunits with comparable efficiency. Furthermore, these two forms of NELF-B have a similar impact on the transcriptomics and proliferation of mouse embryonic fibroblasts. These results strongly suggest that additional amino acid sequence upstream of the annotated AUG is dispensable for the essential function of NELF in supporting cell growth in vitro. While the majority of mouse adult tissues surveyed exclusively express the full-length NELF-B protein, mouse kidney only contains a truncated NELF-B protein with the same apparent size as the AUG-initiated version. This result raises the distinct possibility that translational initiation of mouse NELF-B is regulated in a tissue-dependent manner.
Project description:We performed genome-wide mRNA profiling of 149 human surgical liver samples from Caucasian donors with detailed medical documentation. The overall purpose of the study was to identify expression quantitative trait loci (eQTL) in human liver. 149 liver samples of Caucasian origin were included in the study on the analysis of RNA expression (Illumina Human_WG6_V2) and genotype (HumanHap_300_V1)
Project description:Human and mouse genomes contain a similar number of CpG islands (CGIs), which are discrete CpG-rich DNA sequences associated with transcription start sites. In both species, about 50% of all CGIs are remote from annotated promoters, but nevertheless often have promoter-like features. To document the role of CGI methylation in cell differentiation, we analysed DNA methylation at a comprehensive CGI set in cells of the mouse hematopoietic lineage. Using a method that potentially detects ~33% of genomic CpGs in the methylated state (>7 million) we found that large differences in gene expression were accompanied by surprisingly few DNA methylation changes. There were, however, many DNA methylation differences between hematopoietic cells and a distantly related tissue, brain. Altered DNA methylation occurred predominantly at CGIs within gene bodies, which have the properties of cell type-restricted promoters, but infrequently at annotated gene promoters or CGI flanking sequences. Elevated intragenic CGI methylation correlated with silencing of the associated gene. Differentially methylated intragenic CGIs tended to lack H3K4me3 and associate with a transcriptionally repressive environment regardless of methylation state. Our results indicate that DNA methylation changes play a relatively minor role in the late stages of differentiation, but point to a distinct role for intragenic CGIs. Mouse immune cells (dendritic cells, B cells, CD4 T cells, Th1 and Th2 cells) were isolated and DNA methylation and gene expression profiled. Methylation and expression patterns were compared to those in brain. For gene expression analysis three biological replicates were used for each cell type.
Project description:Jurkat T-cells were latently infected with a defective HIV provirus carrying a GFP reporer gene. The cells were superinfected with a lentiviral vector expressing shRNA to NELF-E. The impact of NELF-depletion on RNAP II distribution on cellular genes and the HIV provirus was measured by ChIP-Seq. Data sets contained between 45 and 56 million mapped reads Four samples were compared: Control shRNA, NELF-E shRNA, Control shRNA plus TNF-a, NELF-E shRNA plus TNF-a.
Project description:Lung cancer is the worldwide leading cause of death from cancer. Tobacco usage is the major pathogenic factor, however, not all lung cancers can be attributable to smoking. The genetic aberrations that differ between smokers' and never-smokersM-bM-^@M-^Y lung carcinomas remain to a large extent unclear. We analyzed 72 early-stage primary lung carcinomas including small cell lung cancers, adenocarcinomas and squamous cell carcinomas by Illumina HT12 gene expression microarrays. Gene expression profiling of 72 lung carcinomas using Illumina HT-12 V3.0 microarrays.