Project description:Deregulation of translational control is an obligatory step in oncogenesis; however, this step has not been addressed by prior genomic and transcriptional profiling studies of cancer biology. Here we simulate the translational deregulation found in cancer by ectopically over expressing translation initiation factor eIF4E in primary human mammary epithelial cells; and examine its impact on cell biology and the pattern of ribosomal recruitment to mRNA genome wide. Over expression of eIF4E allows cells to bypass M0 premature growth arrest, but does not confer other malignant properties. However, in concert with hTERT, eIF4E imparts cells with growth and survival autonomy - and profoundly alters the pattern of polyribosome-associated mRNA encoding cell cycle and apoptosis regulators. The translational response to increased eIF4E is not only a unidirectional activation of oncogenic drivers, but also consists of complex intrinsic translational mechanisms that mitigate the acquisition of neoplastic properties. Keywords: Cell line comparison using both total and polyribosomal RNA
Project description:Combining a genetic and pharmacological approach, we modulated eIF4E activity across its physiological activity range and identified subsets of genes whose translation was either hypo- or hyper- sensitive to eIF4E activity changes. eIF4E hypersensitive genes had longer 5'UTRs with higher GC content; and longer 3'UTRs with lower GC content and a higher density of unique microRNA target sites. Proliferation related genes were enriched among eIF4E hypersensitive genes; and consistent with this, decreasing eIF4E activity inhibited cell cycle transit. Our findings provide genome wide insights into the properties of mRNAs under translational control across the physiological range of eIF4E activity. NIH 3T3 derivatives genetically altered to induce eIF4E when treated with mifepristone and a non-inducible control NIH 3T3 derivative were cultured with or without treatment with mifepristone and varying doses of a pharmacological eIF4E inhibiting agent, 4Ei-1 (0 μM, 10 μM, 50 μM, 100 μM, 200 μM). Total RNA and polyribosome RNA were isolated after 4h of treatment. Three replicates of each experimental group were completed. In addition, three replicates of the inducible cell line treated with less potent analog to the inhibiting agent, 4Ei-4, were completed to probe for non-specific drug effects.
Project description:One common form of translational control is mediated by proteins that bind to the mRNA 5' cap-binding protein eIF4E. These proteins are collectively called 4E binding proteins (4EBPs). Saccharomyces cerevisiae possesses two 4EBPs that are encoded by non-essential genes called CAF20 and EAP1. To determine the impact of gene deletion on gene expression, we monitored the transcript level and also the translation status for each RNA using cycloheximide to freeze elongating ribosomes in wild-type, caf20 and eap1 cells. Polyribosome fractionation of cell extracts was used to separate highly translated and poorly translated mRNAs that were then separately analyzed.
Project description:One common form of translational control is mediated by proteins that bind to the mRNA 5' cap-binding protein eIF4E. These proteins are collectively called 4E binding proteins (4EBPs). Saccharomyces cerevisiae possesses two 4EBPs that are encoded by non-essential genes called CAF20 and EAP1. To determine the impact of gene deletion on gene expression, we monitored the transcript level and also the translation status for each RNA using cycloheximide to freeze elongating ribosomes in wild-type, caf20 and eap1 cells. Polyribosome fractionation of cell extracts was used to separate highly translated and poorly translated mRNAs that were then separately analyzed.
Project description:One of the most regulated steps of translation initiation is the recruitment of an mRNA by the translation machinery. In eukaryotes, this step is mediated by the 5M-BM-4end cap-binding factor eIF4E bound to the bridge protein eIF4G and forming the eIF4F complex. In plants, different isoforms of eIF4E and eIF4G form the antigenically distinct eIF4F and eIF(iso)4F complexes proposed to mediate selective translation. Using a microarray analysis of polyribosome- and non-polyribosome-purified mRNAs from 15 day-old Arabidopsis thaliana wild type [WT] and eIF(iso)4E knockout mutant [AteIF(iso)4E-1] seedlings we found 79 transcripts shifted from polyribosomes toward non-polyribosomes, and 47 mRNAs with the opposite behavior in the mutant. The translationally decreased mRNAs were overrepresented in root-preferentially expressed genes and proteins from the endomembrane system, including several transporters such as the phosphate transporter PHOSPHATE1 (PHO1), Sucrose transporter 3 (SUC3), the ABC transporter-like with ATPase activity (MRP11) and five electron transporters, as well as signal transduction-, protein modification- and transcription-related proteins. For transcriptional analysis used total RNA of AteIF(iso)4E-1 seedlings of 15 days old to known the changes on transcripts leves by the eIF(iso)4E absence, using as control Wt seedlings. The experiments were performed in duplicate, and swap analysis were done. For translational analysis, used non-polysomal and polysomal RNA of AteIF(iso)4E-1 seedlings of 15 days old in order to known the transcripts that are modified in their translational levels by the eIF(iso)4E absence, using as control non polysomal and polysomal RNA of Wt seddlings.
Project description:Aberrant activation of the translation initiation machinery is a common property of malignant cells, and is essential for breast carcinoma cells to manifest a malignant phenotype. How does sustained activation of the rate limiting step in protein synthesis so fundamentally alter a cell? In this report, we test the post transcriptional operon theory as a possible mechanism, employing a model system in which apoptosis resistance is conferred on NIH 3T3 cells by ectopic expression of eIF4E. We show (i) there is a set of 255 transcripts that manifest an increase in translational efficiency during eIF4E-mediated escape from apoptosis; (ii) there is a novel prototype 55 nt RNA consensus hairpin structure that is overrepresented in the 5'-untranslated region of translationally activated transcripts; (iii) the identified consensus hairpin structure is sufficient to target a reporter mRNA for translational activation under pro-apoptotic stress, but only when eIF4E is deregulated; and (iv) that osteopontin, one of the translationally activated transcripts harboring the identified consensus hairpin structure functions as one mediator of the apoptosis resistance seen in our model. Our findings offer genome-wide insights into the mechanism of eIF4E-mediated apoptosis resistance and provide a paradigm for the systematic study of posttranscriptional control in normal biology and disease. Keywords: common reference, various polyribosome fractions
Project description:Introgressed variants from other species can be an important source of genetic variation because they may arise rapidly, can include multiple mutations on a single haplotype, and have often been pretested by selection in the species of origin. Although introgressed alleles are generally deleterious, several studies have reported introgression as the source of adaptive alleles-including the rodenticide-resistant variant of Vkorc1 that introgressed from Mus spretus into European populations of Mus musculus domesticus. Here, we conducted bidirectional genome scans to characterize introgressed regions into one wild population of M. spretus from Spain and three wild populations of M. m. domesticus from France, Germany, and Iran. Despite the fact that these species show considerable intrinsic postzygotic reproductive isolation, introgression was observed in all individuals, including in the M. musculus reference genome (GRCm38). Mus spretus individuals had a greater proportion of introgression compared with M. m. domesticus, and within M. m. domesticus, the proportion of introgression decreased with geographic distance from the area of sympatry. Introgression was observed on all autosomes for both species, but not on the X-chromosome in M. m. domesticus, consistent with known X-linked hybrid sterility and inviability genes that have been mapped to the M. spretus X-chromosome. Tract lengths were generally short with a few outliers of up to 2.7 Mb. Interestingly, the longest introgressed tracts were in olfactory receptor regions, and introgressed tracts were significantly enriched for olfactory receptor genes in both species, suggesting that introgression may be a source of functional novelty even between species with high barriers to gene flow.
Project description:Translational research is commonly performed in the C57B6/J mouse strain, chosen for its genetic homogeneity and phenotypic uniformity. Here, we evaluate the suitability of the white-footed deer mouse (Peromyscus leucopus) as a model organism for aging research, offering a comparative analysis against C57B6/J and diversity outbred (DO) Mus musculus strains. Our study includes comparisons of body composition, skeletal muscle function, and cardiovascular parameters, shedding light on potential applications and limitations of P. leucopus in aging studies. Notably, P. leucopus exhibits distinct body composition characteristics, emphasizing reduced muscle force exertion and a unique metabolism, particularly in fat mass. Cardiovascular assessments showed changes in arterial stiffness, challenging conventional assumptions and highlighting the need for a nuanced interpretation of aging-related phenotypes. Our study also highlights inherent challenges associated with maintaining and phenotyping P. leucopus cohorts. Behavioral considerations, including anxiety-induced responses during handling and phenotyping assessment, pose obstacles in acquiring meaningful data. Moreover, the unique anatomy of P. leucopus necessitates careful adaptation of protocols designed for Mus musculus. While showcasing potential benefits, further extensive analyses across broader age ranges and larger cohorts are necessary to establish the reliability of P. leucopus as a robust and translatable model for aging studies.
Project description:eIF4E, the major cap-binding protein, has long been considered limiting for translating the mammalian genome. However, the requirement for eIF4E dose at an organismal level remains unexplored. By generating an Eif4e haploinsufficient mouse, we surprisingly found that 50% reduction in eIF4E, while compatible with normal development and global protein synthesis, significantly impeded cellular transformation and tumorigenesis. Genome-wide translational profiling uncovered a translational program induced by oncogenic transformation and revealed a critical role for eIF4E dose specifically in translating a network of mRNAs enriched for a unique 5’UTR signature. In particular, we demonstrate that eIF4E dose is essential for translating mRNAs regulating reactive oxygen species (ROS) that fuel transformation and cancer cell survival in vivo. Therefore, mammalian cells have evolved surplus eIF4E levels that cancer cells hijack to drive a translational program supporting tumorigenesis Total cellular RNA and high MW polysome associated RNA were isolated from matched untransformed and transformed WT and Eif4e+/- MEFs for analysis on Affymetrix Mouse Gene 1.0 ST arrays. The difference in log2 RMA intensity between matched polysomal RNA and total RNA was taken to quantify translational efficiency (TE).
Project description:Aberrant activation of the translation initiation machinery is a common property of malignant cells, and is essential for breast carcinoma cells to manifest a malignant phenotype. How does sustained activation of the rate limiting step in protein synthesis so fundamentally alter a cell? In this report, we test the post transcriptional operon theory as a possible mechanism, employing a model system in which apoptosis resistance is conferred on NIH 3T3 cells by ectopic expression of eIF4E. We show (i) there is a set of 255 transcripts that manifest an increase in translational efficiency during eIF4E-mediated escape from apoptosis; (ii) there is a novel prototype 55 nt RNA consensus hairpin structure that is overrepresented in the 5'-untranslated region of translationally activated transcripts; (iii) the identified consensus hairpin structure is sufficient to target a reporter mRNA for translational activation under pro-apoptotic stress, but only when eIF4E is deregulated; and (iv) that osteopontin, one of the translationally activated transcripts harboring the identified consensus hairpin structure functions as one mediator of the apoptosis resistance seen in our model. Our findings offer genome-wide insights into the mechanism of eIF4E-mediated apoptosis resistance and provide a paradigm for the systematic study of posttranscriptional control in normal biology and disease. To globally address the issue of which transcripts mediate the anti-apoptotic functions of eIF4E, we used a model in which NIH 3T3 cells ectopically overexpress translation initiation factor 4E (eIF4E) resulting in an apoptosis-resistant and tumorigenic phenotype. We performed a comprehensive study of apoptosis resistance in the NIH 3T3/4E model using an array containing 15k cDNAs and ESTs (NIH 15k collection printed at The Ontario Cancer Institute). To facilitate data analysis in the two-color competitive hybridization microarray approach employed, we used a universal standard mRNA [non-stratified poly(A) selected RNA derived from NIH 3T3 cells cultured in full growth medium]. We compared signals generated from this standard to both the light (fractions 4â6, <1 ribosome/transcript) and the heavy (fractions 7â10, >1 ribosomes/transcript) polyribosome fractions of RNA from NIH 3T3 and NIH 3T3/4E cells cultured either in complete growth medium or after 16 h of serum starvation, a time point before any evidence of cytochrome c release from the mitochondria, a signature step at the apex of the cell death program. We selected the 16 h time point in order to identify genes that might govern the decision to enter the apoptotic pathway, and exclude those involved in the actual process of cell execution.