As nascent polypeptides exit ribosomes, they are engaged by a series of processing, targeting and folding factors. Here we present a selective ribosome profiling strategy that enables global monitoring of when these factors engage polypeptides in the complex cellular environment. Studies of the Escherichia coli chaperone Trigger Factor (TF) reveal that, while TF can interact with many polypeptides, ß-barrel outer membrane proteins are the most prominent substrates. Loss of TF leads to broad outer membrane defects and premature, cotranslational protein translocation. While in vitro studies suggested that TF is prebound to ribosomes waiting for polypeptides to emerge from the exit channel, we find that in vivo TF engages ribosomes only after ~100 amino acids are translated. Moreover, excess TF interferes with cotranslational removal of the N-terminal formyl methionine. Our studies support a triaging model in which proper protein biogenesis relies on the fine-tuned, sequential engagement of processing, targeting ad folding factors. Overall design: Examination of translation in the Gram-negative bacterium Escherichia coli, as well as an analysis of the interactions between nascent chains and the molecular chaperone Trigger Factor.
Selective ribosome profiling reveals the cotranslational chaperone action of trigger factor in vivo.
Cell line, Subject
View SamplesGenes specific to Sox9+ pancreatic progenitors were identified by comparing the gene expression in embryonic and adult Sox9+ cells.
A Notch-dependent molecular circuitry initiates pancreatic endocrine and ductal cell differentiation.
Specimen part
View SamplesSpinal cord injury leads to impaired motor and sensory functions. After spinal cord injury there is a an initial phase of hypo-reflexia followed by a developing hyper-reflexia, often termed spasticity. Previous studies have suggested a relationship between the reappearence of plateau potentials in motor neurons and the development of spasticity after spinalizaion. To understand the moleclar mechanism behind this pheneomona we examined the transcriptional response of the motor neurons after spinal cord injury as it progress over time.
Transcriptional regulation of gene expression clusters in motor neurons following spinal cord injury.
Sex, Specimen part
View SamplesThe pigmented portion of ciliary epithelium in the adult mammalian eye harbors mitotically quiescent retinal sphere cells, which are capable of self-renewal and differentiating into retinal neurons when assayed in vitro; however, very little is known about the molecular mechanism controlling the proliferation and differentiation of these adult retinal stem cells or their molecular resemblance to mutipotent stem/progenitor cells during early eye development. This experiment studies the gene expression of first passage and primary human and mouse retinal sphere cells.
Recent developments in StemBase: a tool to study gene expression in human and murine stem cells.
Sex
View SamplesThe present study was designed to test the hypothesis that limited growth of the fetal liver in the model of maternal fasting is independent of well-characterized signaling mechanisms that are known to regulate somatic growth in adult animals.
Regulation of fetal liver growth in a model of diet restriction in the pregnant rat.
Specimen part, Treatment
View SamplesSequencing of 5' ends of RNA molecules from control and exosome-depleted HeLa-S3 cells. Overall design: CAGE library construction from RNA extracted from control and exosome-depleted cells.
Nuclear stability and transcriptional directionality separate functionally distinct RNA species.
No sample metadata fields
View SamplesGene expression programs change during cellular transitions. It is well established that a network of transcription factors and chromatin modifiers regulate RNA levels during embryonic stem cell (ESC) differentiation, but the full impact of post-transcriptional processes remains elusive. While cytoplasmic RNA turnover mechanisms have been implicated in differentiation, the contribution of nuclear RNA decay has not been investigated. Here, we differentiate mouse ESCs, depleted for the ribonucleolytic RNA exosome, into embryoid bodies to determine to which degree RNA abundance in the two states can be attributed to changes in transcription vs. RNA decay by the exosome. As a general observation, we find that exosome depletion mainly leads to the stabilization of RNAs from lowly transcribed loci, including several protein-coding genes. In particular, transcripts that are differentially expressed between states tend to be more exosome sensitive in the state where expression is low. We conclude that the RNA exosome contributes to down-regulation of transcripts with disparate expression, often in conjunction with transcriptional down-regulation. Overall design: CAGE experiments were carried out in mouse embryonic stem cells and embryoid bodies differentiated for three days upon depletion of RRP40 with shRNAs, using a scrambled shRNA as control. The experiments were performed in duplicates
The RNA exosome contributes to gene expression regulation during stem cell differentiation.
Specimen part, Cell line, Subject
View SamplesTo investigate genes possibly regulated by TTF-1 in small cell lung cancer cell lines, we compared gene expression profiles of NCI-H209 and Lu139 cell lines electroporated with control and TTF-1 siRNAs.
An integrative transcriptome analysis reveals a functional role for thyroid transcription factor-1 in small cell lung cancer.
Cell line
View SamplesOur strategy was to manipulate mTOR signaling in vivo, then characterize the transcriptome and translating mRNA in liver tissue. In adult rats, we used the non-proliferative growth model of refeeding after a period of fasting, and the proliferative model of liver regeneration following partial hepatectomy. We also studied livers from pre-term fetal rats (embryonic day 19-20) in which fetal hepatocytes are asynchronously proliferating. All three models employed rapamycin to inhibit mTOR signaling.
Profiling of the fetal and adult rat liver transcriptome and translatome reveals discordant regulation by the mechanistic target of rapamycin (mTOR).
Specimen part, Time
View SamplesLiver transplantation is the only therapeutic option for patients with end-stage liver disease. The shortage of donor organs has led to the search for alternative therapies to restore liver function and bridge patients to transplantation. Our previous work has shown that the proliferation of late gestation E19 fetal hepatocytes is mitogen-independent. This is manifested as differences in the control of ribosome biogenesis, global translation, cell cycle progression and gene expression. In the present study, we investigated whether E19 fetal hepatocytes would engraft and repopulate an injured adult liver.
Engraftment and Repopulation Potential of Late Gestation Fetal Rat Hepatocytes.
Specimen part
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