Project description:Integrative genomics positions MKRN1 as a novel ribonucleoprotein within the embryonic stem cell gene regulatory network [RIP-chip]
Project description:In embryonic stem cell (ESCs), gene regulatory networks (GRNs) coordinate gene expression to maintain ESC identity; however, the complete repertoire of factors that regulate the ESC state are not fully understood. Our previous temporal microarray analysis of ESC commitment identified the E3 Ubiquitin Ligase Protein Makorin-1 (MKRN1) as a potential novel component of the ESC GRN. Here, using multilayered systems-level analyses we compiled a MKRN1-centered interactome in undifferentiated ESCs at the proteomic and ribonomic level. Proteomic analyses revealed that MKRN1 is a novel RNA-binding protein that exists within messenger ribonucleoprotein (mRNP) complexes in undifferentiated ESC populations. In accordance with its presence in mRNPs, MKRN1 is mobilized to stress granules (SG) upon arsenite-induced stress, yet MKRN1 is not required for SG formation. RIP-chip analysis revealed that MKRN1 associates with mRNAs encoding functionally related regulatory proteins involved in diverse processes such as cell differentiation, apoptosis, or secreted proteins. Thus, our unbiased systems level analyses supports a role for MKRN1 as a novel RNA-binding protein and a potential gene regulatory protein within the ESC GRN.
Project description:In embryonic stem cell (ESCs), gene regulatory networks (GRNs) coordinate gene expression to maintain ESC identity; however, the complete repertoire of factors that regulate the ESC state are not fully understood. Our previous temporal microarray analysis of ESC commitment identified the E3 Ubiquitin Ligase Protein Makorin-1 (MKRN1) as a potential novel component of the ESC GRN. Here, using multilayered systems-level analyses we compiled a MKRN1-centered interactome in undifferentiated ESCs at the proteomic and ribonomic level. Proteomic analyses revealed that MKRN1 is a novel RNA-binding protein that exists within messenger ribonucleoprotein (mRNP) complexes in undifferentiated ESC populations. In accordance with its presence in mRNPs, MKRN1 is mobilized to stress granules (SG) upon arsenite-induced stress, yet MKRN1 is not required for SG formation. RIP-chip analysis revealed that MKRN1 associates with mRNAs encoding functionally related regulatory proteins involved in diverse processes such as cell differentiation, apoptosis, or secreted proteins. Thus, our unbiased systems level analyses supports a role for MKRN1 as a novel RNA-binding protein and a potential gene regulatory protein within the ESC GRN.
Project description:Chavez2009 - a core regulatory network of OCT4 in human embryonic stem cells
A core OCT4-regulated network has been identified as a test case, to analyase stem cell characteristics and cellular differentiation.
This model is described in the article:
In silico identification of a core regulatory network of OCT4 in human embryonic stem cells using an integrated approach.
Chavez L, Bais AS, Vingron M, Lehrach H, Adjaye J, Herwig R
BMC Genomics, 2009, 10:314
Abstract:
BACKGROUND: The transcription factor OCT4 is highly expressed in pluripotent embryonic stem cells which are derived from the inner cell mass of mammalian blastocysts. Pluripotency and self renewal are controlled by a transcription regulatory network governed by the transcription factors OCT4, SOX2 and NANOG. Recent studies on reprogramming somatic cells to induced pluripotent stem cells highlight OCT4 as a key regulator of pluripotency.
RESULTS: We have carried out an integrated analysis of high-throughput data (ChIP-on-chip and RNAi experiments along with promoter sequence analysis of putative target genes) and identified a core OCT4 regulatory network in human embryonic stem cells consisting of 33 target genes. Enrichment analysis with these target genes revealed that this integrative analysis increases the functional information content by factors of 1.3 - 4.7 compared to the individual studies. In order to identify potential regulatory co-factors of OCT4, we performed a de novo motif analysis. In addition to known validated OCT4 motifs we obtained binding sites similar to motifs recognized by further regulators of pluripotency and development; e.g. the heterodimer of the transcription factors C-MYC and MAX, a prerequisite for C-MYC transcriptional activity that leads to cell growth and proliferation.
CONCLUSION: Our analysis shows how heterogeneous functional information can be integrated in order to reconstruct gene regulatory networks. As a test case we identified a core OCT4-regulated network that is important for the analysis of stem cell characteristics and cellular differentiation. Functional information is largely enriched using different experimental results. The de novo motif discovery identified well-known regulators closely connected to the OCT4 network as well as potential new regulators of pluripotency and differentiation. These results provide the basis for further targeted functional studies.
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Project description:For identification of proteins that associate with Makorin1 (MKRN1) in RNA-dependent and RNA-independent manners, we affinity purified FLAG-tagged Makorin1 (MKRN1) from mouse embryonic stem cells constitutively expressing FLAG:MKRN1. Anti-FLAG control immunoprecipitations were performed from a FLAG vectrol control (FLAG:Ctrl) mouse embryonic stem cell line that did not express FLAG:MKRN1. Following FLAG immunoprecipitation, anti-FLAG beads from FLAG:MKRN1 and FLAG:Ctrl immunoprecipitations were split into separate tubes such that half of the beads were digested with 200Ã∞â≈ Ã≠µg/mL RNase A while the other half of the beads were undigested. RNase A-digested and undigested immunoprecipitates were subjected to LC-MS/MS analysis. Of the 48 RNA-related proteins previously identified to associate with FLAG:MKRN1, L1TD1, PABPC1, PABPC4, YBX1, IGF2BP1 and UPF1 were found to remain associated with FLAG:MKRN1 in the presence of RNase A.
Project description:Makorins are evolutionary conserved proteins that contain C3H-type zinc finger modules and a RING E3 ubiquitin ligase domain. In Drosophila maternal Makorin 1 (Mkrn1) has been linked to embryonic patterning but the mechanism remained unsolved. Here, we show that Mkrn1 is essential for axis specification and pole plasm assembly by translational activation of oskar. We demonstrate that Mkrn1 interacts with poly(A) binding protein (pAbp) and binds specifically to osk 3’ UTR in regions overlapping Bruno1 (Bru1) responsive elements (BREs), which regulate osk translation. We observe increased association of the translational repressor Bru1 with osk mRNA upon depletion of Mkrn1, indicating that both proteins compete for osk binding. Consistently, reducing Bru1 dosage partially rescues viability and Osk protein level in ovaries from Mkrn1 females. We conclude that Mkrn1 controls embryonic patterning and germ cell formation by specifically activating osk translation, most likely by competing with Bru1 to bind to osk 3’ UTR.
Project description:Makorins are evolutionary conserved proteins that contain C3H-type zinc finger modules and a RING E3 ubiquitin ligase domain. In Drosophila maternal Makorin 1 (Mkrn1) has been linked to embryonic patterning but the mechanism remained unsolved. Here, we show that Mkrn1 is essential for axis specification and pole plasm assembly by translational activation of oskar (osk). We demonstrate that Mkrn1 interacts with poly(A) binding protein (pAbp) and binds specifically to osk 3’ UTR in regions overlapping with Bruno1 (Bru1) responsive elements (BREs) that regulate osk translation. We observe increased association of the translational repressor Bru1 with osk mRNA upon depletion of Mkrn1, indicating that both proteins compete for osk binding. Consistently, reducing Bru1 dosage partially rescues viability and Osk protein level in ovaries from Mkrn1 females. We conclude that Mkrn1 controls embryonic patterning and germ cell formation by specifically activating osk translation, most likely by competing with Bru1 to bind to osk 3’ UTR.
Project description:Makorins are an evolutionary conserved family of proteins that contain C3H-type zinc finger modules and a RING E3 ubiquitin ligase domain. Previous analysis indicated a maternal role for Makorin 1 (Mkrn1) in Drosophila embryonic patterning and germ cell specification, but the underlying mechanism has remained elusive. Here, we show that Mkrn1 is specifically required for translational activation of oskar, which encodes a critical regulator of axis specification and germ plasm assembly. We demonstrate that Mkrn1 interacts with poly(A) binding protein (pAbp) and specifically binds osk 3’ UTR adjacent to A-rich sequences. The binding of Mkrn1 to osk 3’UTR occurs in a region that overlaps with Bruno responsive elements (BRE), previously shown to have a dual role in regulating osk translation. We observe an increased association of the translational repressor Bruno (Bru) with osk mRNA upon depletion of Mkrn1, implying that both proteins compete with each other for osk binding. Consistently, reducing Bru dosage is sufficient to partially rescue osk translation and the embryonic lethality associated with Mkrn1 alteration. Thus, we conclude that Mkrn1 controls embryonic patterning and germ cell formation by specifically activating osk translation via displacing Bru from its 3’ UTR
Project description:In this study we affinity purified FLAG-tagged MKRN1 from mouse embryonic stem cells constitutively expressing FLAG:MKRN1 that were pre-treated or untreated with the proteasome inhibitor MG132. FLAG:MKRN1 repeatedly co-immunoprecipitated with 48 proteins irrespective of MG132 treatment. Many of the MKRN1-associated proteins are well-characterized RNA-binding proteins, and post-translational regulators of gene expression.