Showing papers by "Hediye Erdjument-Bromage published in 2013"
TL;DR: It is demonstrated that H2B deubiquitination by USP49 is required for efficient cotranscriptional splicing of a large set of exons and uncovers a critical role for H1A and U1A association with chromatin and binding to nascent pre-mRNA processing events.
Abstract: Post-translational histone modifications play important roles in regulating chromatin structure and function. Histone H2B ubiquitination and deubiquitination have been implicated in transcriptional regulation, but the function of H2B deubiquitination is not well defined, particularly in higher eukaryotes. Here we report the purification of ubiquitin-specific peptidase 49 (USP49) as a histone H2B-specific deubiquitinase and demonstrate that H2B deubiquitination by USP49 is required for efficient cotranscriptional splicing of a large set of exons. USP49 forms a complex with RuvB-like1 (RVB1) and SUG1 and specifically deubiquitinates histone H2B in vitro and in vivo. USP49 knockdown results in small changes in gene expression but affects the abundance of >9000 isoforms. Exons down-regulated in USP49 knockdown cells show both elevated levels of alternative splicing and a general decrease in splicing efficiency. Importantly, USP49 is relatively enriched at this set of exons. USP49 knockdown increased H2B ubiquitination (uH2B) levels at these exons as well as upstream 3′ and downstream 5′ intronic splicing elements. Change in H2B ubiquitination level, as modulated by USP49, regulates U1A and U2B association with chromatin and binding to nascent pre-mRNA. Although H3 levels are relatively stable after USP49 depletion, H2B levels at these exons are dramatically increased, suggesting that uH2B may enhance nucleosome stability. Therefore, this study identifies USP49 as a histone H2B-specific deubiquitinase and uncovers a critical role for H2B deubiquitination in cotranscriptional pre-mRNA processing events.
85 citations
TL;DR: A homology model that unveils a previouslyunknown allosteric site located in the nucleotide binding domain of Hsp70 is developed and a previously unknown inhibitor of this site is discovered, YK5.
85 citations
TL;DR: The multistep mechanism of Rpb1 polyubiquitylation triggered by transcription stress is outlined and the key role played by Def1 as a facilitator of Elongin-Cullin ubiquitin ligase function is uncovered.
76 citations
TL;DR: In this paper, the role of epigenetic regulators in hematopoiesis has become critically important, because recurrent mutations or aberrant expression of these genes has been identified in both myeloid and lymphoid hematological malignancies.
74 citations
26 Dec 2013
TL;DR: It is found that PRMT4, a type I arginine methyltransferase whose function in normal and malignant hematopoiesis is unknown, is overexpressed in acute myelogenous leukemia patient samples and holds potential as a novel therapy for acute myELogenous leukemia.
Abstract: SUMMARY Defining the role of epigenetic regulators in hematopoiesis has become critically important, because recurrent mutations or aberrant expression of these genes has been identified in both myeloid and lymphoid hematological malignancies. We found that PRMT4, a type I arginine methyltransferase whose function in normal and malignant hematopoiesis is unknown, is overexpressed in acute myelogenous leukemia patient samples. Overexpression of PRMT4 blocks the myeloid differentiation of human stem/progenitor cells (HSPCs), whereas its knockdown is sufficient to induce myeloid differentiation of HSPCs. We demonstrated that PRMT4 represses the expression of miR-223 in HSPCs via the methylation of RUNX1, which triggers the assembly of a multiprotein repressor complex that includes DPF2. As part of the feedback loop, PRMT4 expression is repressed posttranscriptionally by miR-223. Depletion of PRMT4 results in differentiation of myeloid leukemia cells in vitro and their decreased proliferation in vivo. Thus, targeting PRMT4 holds potential as a novel therapy for acute myelogenous leukemia.
70 citations
TL;DR: It is found that lymphoma cells infected by Epstein-Barr virus or Kaposi sarcoma-associated herpes virus (KSHV) are exquisitely sensitive to this compound, and PU-H71 affinity capture identifies actionable networks that may help design rational combinations of effective therapies.
66 citations
TL;DR: The functional significance of FLNB K1147 to interfere with the ability of phorbol myristate acetate (PMA) to promote FLNB-mediated cytoplasmic accumulation of HDAC7 is demonstrated.
Abstract: Nucleocytoplasmic shuttling of class IIa of histone deacetylases (HDACs) is a key mechanism that controls cell fate and animal development. We have identified the filamin B (FLNB) as a novel HDAC7-interacting protein that is required for temporal and spatial regulation of vascular endothelial growth factor (VEGF)-mediated HDAC7 cytoplasmic sequestration. This interaction occurs in the cytoplasm and requires monoubiquitination of an evolutionarily conserved lysine 1147 (K1147) in the immunoglobulin (Ig)-like repeat 10 (R10) of FLNB and the nuclear localization sequence of HDAC7. Inhibition of protein kinase C (PKC) blocks VEGF-induced ubiquitination of FLNB and its interaction with HDAC7. Small interfering RNA (siRNA) knockdown of FLNB or ubiquitin (Ub) in human primary endothelial cells blocks VEGF-mediated cytoplasmic accumulation of HDAC7, reduces VEGF-induced expression of the HDAC7 target genes Mmp-10 and Nur77, and inhibits VEGF-induced vascular permeability. Using dominant negative mutants and rescue experiments, we demonstrate the functional significance of FLNB K1147 to interfere with the ability of phorbol myristate acetate (PMA) to promote FLNB-mediated cytoplasmic accumulation of HDAC7. Taken together, our data show that VEGF and PKC promote degradation-independent protein ubiquitination of FLNB to control intracellular trafficking of HDAC7.
26 citations
TL;DR: It is suggested that FBXW4 may be a novel tumor suppressor that regulates important cellular processes and is mutated, lost and under-expressed in a variety of human cancer cell lines and clinical patient samples.
Abstract: Identification of novel proteins that can potentially contribute to carcinogenesis is a requisite venture. Herein, we report the first biochemical characterization of the novel F-box and WD40 containing protein, FBXW4. We have identified interacting protein partners and demonstrated that FBXW4 is part of a ubiquitin ligase complex. Furthermore, the Fbxw4 locus is a common site of proviral insertion in a variety of retroviral insertional mutagenesis murine cancer models and Fbxw4 mRNA is highly expressed in the involuting murine mammary gland. To begin to characterize the biochemical function of Fbxw4, we used proteomic analysis to demonstrate that Fbxw4 interacts with Skp1 (SKP1), Cullin1 (CUL1), Ring-box1 (RBX1) and all components of the COP9 signalosome. All of these interactions are dependent on an intact F-box domain of Fbxw4. Furthermore, Fbxw4 is capable of interacting with ubiquitinated proteins within cells in an F-box dependent manner. Finally, we demonstrate that FBXW4 is mutated, lost and under-expressed in a variety of human cancer cell lines and clinical patient samples. Importantly, expression of FBXW4 correlates with survival of patients with non-small cell lung cancer. Taken together, we suggest that FBXW4 may be a novel tumor suppressor that regulates important cellular processes.
23 citations
TL;DR: An expression system for producing the full-length human EphA2 receptor is developed and the purified receptor was shown to retain its biological activity in terms of both binding to its functional ligands and being able to auto-phosphorylate the key tyrosine residues of the cytoplasmic kinase domain.
8 citations