Browsing by Subject "Repressor Proteins"

Now showing 1 - 9 of 9
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    An enhancer- blocking element regulates the cell-specific expression of alcohol dehydrogenase 7
    (Elsevier, 2014-09-01) Jairam, Sowmya; Edenberg, Howard J.; Department of Biochemistry and Molecular Biology, IU School of Medicine
    The class IV alcohol dehydrogenase gene ADH7 encodes an enzyme that is involved in ethanol and retinol metabolism. ADH7 is expressed mainly in the upper gastrointestinal tract and not in the liver, the major site of expression of the other closely related ADHs. We identified an intergenic sequence (iA1C), located between ADH7 and ADH1C, that has enhancer-blocking activity in liver-derived HepG2 cells that do not express their endogenous ADH7. This enhancer blocking function was cell- and position-dependent, with no activity seen in CP-A esophageal cells that express ADH7 endogenously. iA1C function was not specific to the ADH enhancers; it had a similar cell-specific effect on the SV40 enhancer. The CCCTC-binding factor (CTCF), an insulator binding protein, bound iA1C in HepG2 cells but not in CP-A cells. Our results suggest that in liver-derived cells, iA1C blocks the effects of ADH enhancers and thereby contributes to the cell specificity of ADH7 expression.
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    Loss of Asxl1 leads to myelodysplastic syndrome-like disease in mice
    (American Society of Hematology, 2014-01-23) Wang, Jiapeng; Li, Zhaomin; He, Yongzheng; Pan, Feng; Chen, Shi; Rhodes, Steven; Nguyen, Lihn; Yuan, Jin; Jiang, Li; Yang, Xianlin; Weeks, Ophelia; Liu, Ziyue; Zhou, Jiehao; Ni, Hongyu; Cai, Chen-Leng; Xu, Mingjiang; Yang, Feng-Chun; Department of Biostatistics, School of Public Health
    ASXL1 is mutated/deleted with high frequencies in multiple forms of myeloid malignancies, and its alterations are associated with poor prognosis. De novo ASXL1 mutations cause Bohring-Opitz syndrome characterized by multiple congenital malformations. We show that Asxl1 deletion in mice led to developmental abnormalities including dwarfism, anophthalmia, and 80% embryonic lethality. Surviving Asxl1(-/-) mice lived for up to 42 days and developed features of myelodysplastic syndrome (MDS), including dysplastic neutrophils and multiple lineage cytopenia. Asxl1(-/-) mice had a reduced hematopoietic stem cell (HSC) pool, and Asxl1(-/-) HSCs exhibited decreased hematopoietic repopulating capacity, with skewed cell differentiation favoring granulocytic lineage. Asxl1(+/-) mice also developed mild MDS-like disease, which could progress to MDS/myeloproliferative neoplasm, demonstrating a haploinsufficient effect of Asxl1 in the pathogenesis of myeloid malignancies. Asxl1 loss led to an increased apoptosis and mitosis in Lineage(-)c-Kit(+) (Lin(-)c-Kit(+)) cells, consistent with human MDS. Furthermore, Asxl1(-/-) Lin(-)c-Kit(+) cells exhibited decreased global levels of H3K27me3 and H3K4me3 and altered expression of genes regulating apoptosis (Bcl2, Bcl2l12, Bcl2l13). Collectively, we report a novel ASXL1 murine model that recapitulates human myeloid malignancies, implying that Asxl1 functions as a tumor suppressor to maintain hematopoietic cell homeostasis. Future work is necessary to clarify the contribution of microenvironment to the hematopoietic phenotypes observed in the constitutional Asxl1(-/-) mice.
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    Reply.
    (Wiley, 2015-10) Nho, Kwangsik; Saykin, Andrew J.; Department of Radiology and Imaging Sciences, IU School of Medicine
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    Reply: To PMID 25559091
    (Wiley Blackwell (John Wiley & Sons), 2015-11) Nho, Kwangsik; Farrer, Lindsay A.; Saykin, Andrew J.; Department of Radiology and Imaging Sciences, IU School of Medicine
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    RPRD1A and RPRD1B Are Human RNA Polymerase II C-Terminal Domain Scaffolds for Ser5 Dephosphorylation
    (Nature Publishing Group, 2014-08) Ni, Zuyao; Xu, Chao; Guo, Xinghua; Hunter, Gerald O.; Kuznetsova, Olga V.; Tempel, Wolfram; Marcon, Edyta; Zhong, Guoqing; Guo, Hongbo; Kuo, Wei-Hung William; Li, Joyce; Young, Peter; Olsen, Jonathan B.; Wan, Cuihong; Loppnau, Peter; El Bakkouri, Majida; Senisterra, Guillermo A.; He, Hao; Huang, Haiming; Sidhu, Sachdev S.; Emili, Andrew; Murphy, Shona; Mosley, Amber L.; Arrowsmith, Cheryl H.; Min, Jinrong; Greenblatt, Jack F.; Department of Biochemistry & Molecular Biology, IU School of Medicine
    The RNA polymerase II (RNAPII) carboxyl-terminal domain (CTD) heptapeptide repeats (Y1-S2-P3-T4-S5-P6-S7) undergo dynamic phosphorylation and dephosphorylation during the transcription cycle to recruit factors that regulate transcription, RNA processing and chromatin modification. We show here that RPRD1A and RPRD1B form homodimers and heterodimers through their coiled-coil domains and interact preferentially via CTD interaction domains (CIDs) with CTD repeats phosphorylated at S2 and S7. Our high resolution crystal structures of the RPRD1A, RPRD1B and RPRD2 CIDs, alone and in complex with CTD phosphoisoforms, elucidate the molecular basis of CTD recognition. In an interesting example of cross-talk between different CTD modifications, our data also indicate that RPRD1A and RPRD1B associate directly with RPAP2 phosphatase and, by interacting with CTD repeats where phospho-S2 and/or phospho-S7 bracket a phospho-S5 residue, serve as CTD scaffolds to coordinate the dephosphorylation of phospho-S5 by RPAP2.
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    SPOP Promotes Ubiquitination and Degradation of the ERG Oncoprotein to Suppress Prostate Cancer Progression
    (Elsevier, 2015-09-17) Gan, Wenjian; Dai, Xiangpeng; Lunardi, Andrea; Li, Zhen; Inuzuka, Hiroyuki; Liu, Pengda; Varmeh, Shoreh; Zhang, Jinfang; Cheng, Liang; Sun, Yin; Asara, John M.; Beck, Andrew H.; Huang, Jiaoti; Pandolfi, Pier Paolo; Wei, Wenyi; Department of Pathology and Laboratory Medicine, IU School of Medicine
    The ERG gene is fused to TMPRSS2 in approximately 50% of prostate cancers (PrCa), resulting in its overexpression. However, whether this is the sole mechanism underlying ERG elevation in PrCa is currently unclear. Here we report that ERG ubiquitination and degradation are governed by the Cullin 3-based ubiquitin ligase SPOP and that deficiency in this pathway leads to aberrant elevation of the ERG oncoprotein. Specifically, we find that truncated ERG (ΔERG), encoded by the ERG fusion gene, is stabilized by evading SPOP-mediated destruction, whereas prostate cancer-associated SPOP mutants are also deficient in promoting ERG ubiquitination. Furthermore, we show that the SPOP/ERG interaction is modulated by CKI-mediated phosphorylation. Importantly, we demonstrate that DNA damage drugs, topoisomerase inhibitors, can trigger CKI activation to restore the SPOP/ΔERG interaction and its consequent degradation. Therefore, SPOP functions as a tumor suppressor to negatively regulate the stability of the ERG oncoprotein in prostate cancer.
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    Survivin Modulates Genes with Divergent Molecular Functions and Regulates Proliferation of Hematopoietic Stem Cells through Evi-1
    (Nature Publishing Group, 2015-02) Fukuda, Seiji; Hoggatt, Jonathan; Singh, Pratibha; Abe, Mariko; Speth, Jennifer M.; Hu, Peirong; Conway, Edward M.; Nucifora, Giuseppina; Yamaguchi, Seiji; Pelus, Louis M.; Department of Microbiology & Immunology, IU School of Medicine
    The inhibitor of apoptosis protein Survivin regulates hematopoiesis, although its mechanisms of regulation of hematopoietic stem cells (HSCs) remain largely unknown. While investigating conditional Survivin deletion in mice, we found that Survivin was highly expressed in phenotypically defined HSCs and Survivin deletion in mice resulted in significantly reduced total marrow HSC and progenitor cells (HPC). Transcriptional analysis of Survivin−/− HSCs revealed altered expression of multiple genes not previously linked to Survivin activity. In particular, Survivin deletion significantly reduced expression of the Evi-1 transcription factor indispensable for HSC function, and the downstream Evi-1 target genes Gata2, Pbx1 and Sall2. The loss of HSCs following Survivin deletion and impaired long-term HSC repopulating function could be partially rescued by ectopic Evi-1 expression in Survivin −/− HSCs. These data demonstrate that Survivin partially regulates HSC function by modulating the Evi-1transcription factor and its downstream targets and identify new genetic pathways in HSCs regulated by Survivin.
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    Survivin-induced abnormal ploidy contributes to cystic kidney and aneurysm formation
    (Ovid Technologies Wolters Kluwer -American Heart Association, 2014-02-11) AbouAlaiwi, Wissam A.; Muntean, Brian S.; Ratnam, Shobha; Joe, Bina; Liu, Lijun; Booth, Robert L.; Rodriguez, Ingrid; Herbert, Britney S.; Bacallao, Robert L.; Fruttiger, Marcus; Mak, Tak W.; Zhou, Jing; Nauli, Surya M.; Department of Medical and Molecular Genetics, IU School of Medicine
    BACKGROUND: Cystic kidneys and vascular aneurysms are clinical manifestations seen in patients with polycystic kidney disease, a cilia-associated pathology (ciliopathy). Survivin overexpression is associated with cancer, but the clinical pathology associated with survivin downregulation or knockout has never been studied before. The present studies aim to examine whether and how cilia function (Pkd1 or Pkd2) and structure (Tg737) play a role in cystic kidney and aneurysm through survivin downregulation. METHODS AND RESULTS: Cysts and aneurysms from polycystic kidney disease patients, Pkd mouse, and zebrafish models are characterized by chromosome instability and low survivin expression. This triggers cytokinesis defects and formation of nuclear polyploidy or aneuploidy. In vivo conditional mouse and zebrafish models confirm that survivin gene deletion in the kidneys results in a cystic phenotype. As in hypertensive Pkd1, Pkd2, and Tg737 models, aneurysm formation can also be induced in vascular-specific normotensive survivin mice. Survivin knockout also contributes to abnormal oriented cell division in both kidney and vasculature. Furthermore, survivin expression and ciliary localization are regulated by flow-induced cilia activation through protein kinase C, Akt and nuclear factor-κB. Circumventing ciliary function by re-expressing survivin can rescue polycystic kidney disease phenotypes. CONCLUSIONS: For the first time, our studies offer a unifying mechanism that explains both renal and vascular phenotypes in polycystic kidney disease. Although primary cilia dysfunction accounts for aneurysm formation and hypertension, hypertension itself does not cause aneurysm. Furthermore, aneurysm formation and cyst formation share a common cellular and molecular pathway involving cilia function or structure, survivin expression, cytokinesis, cell ploidy, symmetrical cell division, and tissue architecture orientation.
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    TG-interacting factor 1 (Tgif1)-deficiency attenuates bone remodeling and blunts the anabolic response to parathyroid hormone
    (Nature Research, 2019-03-22) Saito, Hiroaki; Gasser, Andreas; Bolamperti, Simona; Maeda, Miki; Matthies, Levi; Jähn, Katharina; Long, Courtney L.; Schlüter, Hartmut; Kwiatkowski, Marcel; Saini, Vaibhav; Pajevic, Paola Divieti; Bellido, Teresita; Wijnen, Andre J. van; Mohammad, Khalid S.; Guise, Theresa A.; Taipaleenmäki, Hanna; Hesse, Eric; Anatomy and Cell Biology, School of Medicine
    Osteoporosis is caused by increased bone resorption and decreased bone formation. Intermittent administration of a fragment of Parathyroid hormone (PTH) activates osteoblast-mediated bone formation and is used in patients with severe osteoporosis. However, the mechanisms by which PTH elicits its anabolic effect are not fully elucidated. Here we show that the absence of the homeodomain protein TG-interacting factor 1 (Tgif1) impairs osteoblast differentiation and activity, leading to a reduced bone formation. Deletion of Tgif1 in osteoblasts and osteocytes decreases bone resorption due to an increased secretion of Semaphorin 3E (Sema3E), an osteoclast-inhibiting factor. Tgif1 is a PTH target gene and PTH treatment failed to increase bone formation and bone mass in Tgif1-deficient mice. Thus, our study identifies Tgif1 as a novel regulator of bone remodeling and an essential component of the PTH anabolic action. These insights contribute to a better understanding of bone metabolism and the anabolic function of PTH.