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Reversible mRNA and miRNA expression patterns in the transcriptome of Rasless fibroblasts

ABSTRACT: Analysis of the transcriptional profiles of mRNA and microRNA in Rasless fibroblasts. 4-Hydroxy-tamoxifen (4-OHT) treatment triggers removal of K-Ras expression in [H-Ras-/-;N-Ras-/-;K-Raslox/lox;RERTert/ert ] mouse fibroblasts (named K-Raslox) generating “Rasless” MEFs which are unable to proliferate, but recover proliferative ability after ectopic expression of constitutively active downstream kinases such as BRAF and MEK1. Using Affymetrix microarrays, we compared the transcriptional profiles of Rasless fibroblasts to those of K-Raslox (MEFs lacking only H-Ras and N-Ras). We also compared the transcriptional profile of Rasless cells with those of BRAF and MEK1-transfected Rasless cells which recovered proliferative ability. Re-entry of the Rasless cells into cell cycle progression through ectopic expression of activated BRAF or MEK1 resulted in full reversion of most transcriptional alterations identified in cells lacking the three canonical Ras proteins.

ORGANISM(S): Mus musculus synthetic construct

PROVIDER: GSE45222 | GEO | 2013/11/27

SECONDARY ACCESSION(S): PRJNA193231

REPOSITORIES: GEO

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Project description:Analysis of the transcriptional profiles of mRNA and microRNA in Rasless fibroblasts. 4-Hydroxy-tamoxifen (4-OHT) treatment triggers removal of K-Ras expression in [H-Ras-/-;N-Ras-/-;K-Raslox/lox;RERTert/ert] mouse fibroblasts (named K-Raslox) generating M-bM-^@M-^\RaslessM-bM-^@M-^] MEFs which are unable to proliferate, but recover proliferative ability after ectopic expression of constitutively active downstream kinases such as BRAF and MEK1. Using Affymetrix microarrays, we compared the transcriptional profiles of Rasless fibroblasts to those of K-Raslox (MEFs lacking only H-Ras and N-Ras). We also compared the transcriptional profile of Rasless cells with those of BRAF and MEK1-transfected Rasless cells which recovered proliferative ability. Re-entry of the Rasless cells into cell cycle progression through ectopic expression of activated BRAF or MEK1 resulted in full reversion of most transcriptional alterations identified in cells lacking the three canonical Ras proteins. Pre-confluent cell cultures corresponding to the different Ras genotypes were harvested for extraction of total RNA and miRNA samples, and subsequent hybridization on Affymetrix microarrays. The different sets of experimental mRNA samples analyzed here included (i) 8 samples K-Raslox (proliferating cells expressing only K-Ras, considered as Control): 4 biological replicates, technical duplicates each; (ii) 7 samples Rasless: the same cells after treatment with 4-OHT for 12 days (to become non-proliferating fibroblasts), including 4 biological replicates and technical duplicates from 3 of them; (iii) 3 samples BRAF-rescued MEFs (Rasless cells harboring activated BRAF constructs, with regained proliferative ability): 3 biological replicates; (iv) 3 samples MEK1-rescued MEFs (Rasless cells harboring activated MEK1 constructs, with regained proliferative ability): 3 biological replicates; and their respective controls harbouring the vempty vectors (v) 2 samples Hygromycin-resistant (control for BRAF-transfected Rasless cells) including 2 biological replicates, and (vi) 4 samples Puromycin-resistant (control for MEK1-transfected Rasless cells) including 2 biological replicates, technical duplicates each. The gene expression study contains a total of 27 samples. Regarding the miRNA expression study, the experimental samples analyzed included (i) 4 samples samples K-Raslox (used as Control): 2 biological replicates, technical duplicates each; (ii) 8 samples Rasless: the same cells after treatment with 4-OHT for 6 days (2 biological replicates, technical duplicates each) and 12 days (2 biological replicates, technical duplicates each); (iii) 4 samples BRAF-rescued, including 2 biological replicates, technical duplicates each; (iv) 4 samples MEK1-rescued,including 2 biological replicates, technical duplicates each, and (v) 4 samples Puromycin-resistant empty vector, containing 2 biological replicates, technical duplicates each. The miRNA expression study contains a total of 24 samples.

Project description:Ras plays roles across the spectrum of proliferation, invasion and metastasis. The activity of Ras genes, usually K-Ras, is altered by mutations in around 20% of human cancers, and activation of the Ras-ERK pathway is a critical event in melanomas, colorectal and renal cancers but the degree to which Ras- or Raf-driven transformation is dependent on the activity of the SRF network remains largely obscure. Oncogenic active Ras is known to mediate the cellular response to multiple growth factors leading to the activation of immediate-early genes (IE). A key player in IE gene response is the SRF transcriptional network that we identified being crucial to mediate allegedly the entire transcriptional response downstream of Ras/ERK. The Serum response factor (SRF) is a transcription factor with low intrinsic transcriptional activity and requires the recruitment of one of two families of co-activators: the MRTFs (myocardin-related transcription factors) and the TCFs (ternary complex factors, Elk-1, SAP-1, Net). In particular the TCF, member of the wide family of ETS transcription factors, are specifically activated by MAPK signalling downstream of Ras. We characterised the transcriptional program downstream of Ras/ERK signalling using short TPA stimulations (12-O-tetradecanoyl phorbol-13-acetate, compunt known to induced Ras/ERK activation) by RNA-seq. The investigation of the transcriptional response was performed using Mouse Embryonic Fibroblasts (MEFs) derived from different animals: (i) wild type, (ii) TKO (MEFs derived from mice lacking all three TCFs), (iiI) TKO recon pMY Empty (TKO reconstituted with empty vectors by retrovirus infection), (iv) TKO recon Elk-1 wt (TKO reconstituted with retrovirus vectors expressing Elk-1 wild type by retrovirus infection), (v) TKO recon Elk-1 FW (TKO reconstituted with retrovirus vectors expressing Elk-1 mutant lacking the FW residues in its activation domain), (vi) TKO recon Elk-1 nonA (TKO reconstituted with retrovirus vectors expressing Elk-1 mutant where all phosphor-acceptor residues in its activation domain have been mutagenized to alanines). In order to map SRF and Elk-1 binding sites we performed ChIP-seq of SRF in wild type MEFs and TKO and ChIP-seq of Elk-1 in TKO reconstituted cell lines.

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Reversible mRNA and miRNA expression patterns in the transcriptome of Rasless fibroblasts

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