Unknown,Transcriptomics,Genomics,Proteomics

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Enhanced CLIP uncovers IMP protein-RNA targets in human pluripotent stem cells important for cell adhesion and survival [eCLIP-Seq]

ABSTRACT: Human pluripotent stem cells (hPSCs) require precise control of post-transcriptional RNA networks to maintain proliferation and survival. Using a recently developed enhanced UV crosslinking and immunoprecipitation (eCLIP) approach, we identify RNA targets of the IMP/IGF2BP family of RNA-binding proteins in hPSCs. At the broad region- and binding site-level IMP1 and IMP2 show reproducible binding to a large and overlapping set of 3'UTR-enriched targets. RNA Bind-N-Seq applied to recombinant full-length IMP1 and IMP2 reveals CA-rich motifs that are enriched in eCLIP-defined binding sites. We observe that IMP1 loss in hPSCs recapitulates IMP1 phenotypes, including a reduction in cell adhesion and an increase in cell death. For cell adhesion, in hPSCs we find IMP1 maintains levels of integrin mRNA, specifically regulating RNA stability of ITGB5. Additionally, we show IMP1 can be linked to hPSC survival via direct target BCL2. Thus, transcriptome-wide binding profiles identify hPSC targets modulating well-characterized IMP1 roles. eCLIP-seq was performed in biological replicate for IGF2BP1/IMP1 and IGF2BP2/IMP2, as well as one replicate each for IGF2BP3/IMP3, RBFOX2, and an IgG control. Each sample has a size-matched input control for analysis

ORGANISM(S): Homo sapiens

SUBMITTER: Gene Yeo

PROVIDER: E-GEOD-78507 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Human pancreatic stellate cells (HPSCs) are an essential stromal component and are the mediators of pancreatic ductal adenocarcinoma (PDAC) progression. Small extracellular vesicles (sEVs) are membrane-enclosed nanoparticles released from stellate cells adjacent to the PDAC. sEVs are believed to play a key role in cell-cell communications and may play a critical role in disease progression. The role of membrane proteins of HPSC sEVs in the PDAC tumor microenvironment is unclear and to date, there has not been a quantitative proteomic comparison of sEVs from normal pancreatic stellate cells (HPaStec) and from PDAC-associated stellate cells (HPSCs). We hypothesized there would be differences in sEVs secretion and membrane protein expression between the 2 conditions that might contribute to PDAC biology. To test these hypotheses, we isolated sEVs using ultracentrifugation followed by characterization by electron microscopy and Nanoparticle Tracking Analysis. HPSCs secreted more sEVs compared to HPaStec, and these sEVs were enriched with exosomal markers, which was confirmed by Western blotting and flow cytometry. HPSC-sEVs also restore the activation of normal stellate cells. Next, we showed that intact membrane-associated proteins may be essential for sufficient uptake of stellate cell sEVs by both normal epithelial and cancer cells. Importantly, we demonstrated that stellate cells in general modulate the cellular proliferations of pancreatic cancer cells although stellate cell sEVs did not change the proliferation of cancer cells. We then compared sEV proteins isolated from HPSCs and HPaStecs cells using liquid chromatography–tandem mass spectrometry. Most of the 1,481 protein groups identified were shared with the exosome database, ExoCarta (http://exocarta.org/; curated by the Mathivanan Lab). Eighty-seven protein groups were differentially expressed (selected by 2-fold difference and adjusted P value ≤ 0.05) between HPSC and HPaStec sEVs. HPSC sEVs contained dramatically more CSE1L, a poor prognostic marker for pancreatic cancer. In conclusion, our findings using mass spectrometry–based proteomics may direct further studies to understand the biology and role of protein composition of HPSC sEVs in PDAC progression or to develop novel strategies based on delivery of exosome cargo to PDAC tumor cells.

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Enhanced CLIP uncovers IMP protein-RNA targets in human pluripotent stem cells important for cell adhesion and survival [eCLIP-Seq]

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