Unknown,Transcriptomics,Genomics,Proteomics

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Expression analysis of p53-/- and p53-/-, Ha-RasV12-transformed MEFs upon E4F1 gene inactivation

ABSTRACT: E4F1 is a ubiquitously expressed zinc-finger protein of the Gli-Kruppel family that was first identified, more than 30 years ago, as a cellular target of the adenoviral oncoprotein E1A13S (Ad type V), required for transcriptional regulation of adenoviral genes. In order to identify the p53-independent program controlled by E4F1, we performed microarray analyses in p53 KO and p53 KO; Ha-RasV12-transformed mouse embryonic fibroblasts (MEFs) in wild type and E4F1-inactivated cells. To address p53-independent E4F1 transcriptome, a 12 chip array study has been realized using total RNA recovered from wild-type (E4F1+/flox, CRE infected; odd Samples) MEFs and E4F1-depleted (E4F1-/flox, CRE infected; even Samples) MEFs in p53-/- (Samples 1 to 12) and p53-/-, Ha-RasV12 background (Samples 13 to 24). p53-/- MEFs were derived from 13.5-day mouse embryos. Transformed p53-/- MEFs were generated by infection with a recombinant retrovirus encoding for Ha-RasV12. Three independent biological replicates of wild-type and knock-out MEFs for E4F1 have been used on the two genetic backgrounds.

ORGANISM(S): Mus musculus

SUBMITTER: Claude Sardet

PROVIDER: E-GEOD-57240 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The t(11;22)(p13;q12) translocation is pathognomonic for the highly aggressive desmoplastic small round cell tumour (DSRCT). The translocation fuses exon 7 of the EWS gene to exon 8 of the WT1 gene (EWS/WT1). Two splice variants of EWS/WT1 exist, arising from the presence (+KTS) or absence (-KTS) of three amino acids: lysine, threonine and serine between zinc fingers 3 and 4. To investigate the oncogenic properties of both isoforms of EWS/WT1, we over-expressed EWS/WT1 in untransformed murine embryonic fibroblasts (MEFs). We demonstrate that neither isoform of EWS/WT1 is sufficient to transform wild type MEFs, however the oncogenic potential of both isoforms is unmasked by the loss of p53. Expression of EWS/WT1 in MEFs lacking at least one allele of p53 resulted in enhanced cell proliferation, clonogenic survival and anchorage-independent growth. In addition EWS/WT1 expression in wild type MEFs attenuated several p53-dependent responses, including cell cycle arrest after irradiation and daunorubicin induced apoptosis. We show that DSRCT commonly have copy number amplification of MDM2 and MDMX, suggesting loss of p53 function in the tumours. Expression of either isoform of EWS/WT1 in MEFs induced characteristic mRNA expression profiles, including up-regulation of canonical Wnt pathway signaling. This was validated in cell lines and in a series of DSCRT, which confirmed canonical Wnt pathway activation in the tumours. We show for the first time that both isoforms of EWS/WT1 have oncogenic potential and that in addition to co-operating with loss of p53 function can also further attenuate p53-mediated responses. In addition we provide the first link between EWS/WT1 and Wnt pathway signaling. These data provide novel insights into the function of the EWS/WT1 fusion protein which characterizes DSCRT. Four independently generated pools of wild type MEFs were infected with tetracycline repressible EWS/WT1+KTS, EWS/WT1-KTS or GFP, selected with hygromycin and protein expression confirmed. Four GFP, four KTS+ and four KTS- samples were hybridized to the Ilumina BeadChip.

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Expression analysis of p53-/- and p53-/-, Ha-RasV12-transformed MEFs upon E4F1 gene inactivation

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