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Kim M, Civin CI, Kingsbury TJ. MicroRNAs as regulators and effectors of hematopoietic transcription factors. WILEY INTERDISCIPLINARY REVIEWS-RNA 2019; 10:e1537. [PMID: 31007002 DOI: 10.1002/wrna.1537] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 03/24/2019] [Accepted: 04/03/2019] [Indexed: 12/17/2022]
Abstract
Hematopoiesis is a highly-regulated development process orchestrated by lineage-specific transcription factors that direct the generation of all mature blood cells types, including red blood cells, megakaryocytes, granulocytes, monocytes, and lymphocytes. Under homeostatic conditions, the hematopoietic system of the typical adult generates over 1011 blood cells daily throughout life. In addition, hematopoiesis must be responsive to acute challenges due to blood loss or infection. MicroRNAs (miRs) cooperate with transcription factors to regulate all aspects of hematopoiesis, including stem cell maintenance, lineage selection, cell expansion, and terminal differentiation. Distinct miR expression patterns are associated with specific hematopoietic lineages and stages of differentiation and functional analyses have elucidated essential roles for miRs in regulating cell transitions, lineage selection, maturation, and function. MiRs function as downstream effectors of hematopoietic transcription factors and as upstream regulators to control transcription factor levels. Multiple miRs have been shown to play essential roles. Regulatory networks comprised of differentially expressed lineage-specific miRs and hematopoietic transcription factors are involved in controlling the quiescence and self-renewal of hematopoietic stem cells as well as proliferation and differentiation of lineage-specific progenitor cells during erythropoiesis, myelopoiesis, and lymphopoiesis. This review focuses on hematopoietic miRs that function as upstream regulators of central hematopoietic transcription factors required for normal hematopoiesis. This article is categorized under: RNA in Disease and Development > RNA in Development Regulatory RNAs/RNAi/Riboswitches > Regulatory RNAs.
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Affiliation(s)
- MinJung Kim
- Department of Pediatrics, Center for Stem Cell Biology and Regenerative Medicine, Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland
| | - Curt I Civin
- Department of Pediatrics and Physiology, Center for Stem Cell Biology and Regenerative Medicine, Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland
| | - Tami J Kingsbury
- Department of Physiology, Center for Stem Cell Biology and Regenerative Medicine, Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland
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Burst V, Pütsch F, Kubacki T, Völker LA, Bartram MP, Müller RU, Gillis M, Kurschat CE, Grundmann F, Müller-Ehmsen J, Benzing T, Teschner S. Survival and distribution of injected haematopoietic stem cells in acute kidney injury. Nephrol Dial Transplant 2012. [PMID: 23197679 DOI: 10.1093/ndt/gfs513] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND Endogenous bone marrow-derived cells are known to incorporate into renal epithelium at a low rate. Haematopoietic stem cells (HSCs) rather than mesenchymal stem cells (MSC) are responsible for this phenomenon. MSCs have the potential to ameliorate kidney function after acute kidney injury (AKI) without directly repopulating the tubules. However, little is known about the short-term effect of HSCs. METHODS In this article, we analysed the survival rate and organ distribution of isolated rat HSCs injected into the renal artery after ischaemic renal injury, using quantitative real-time PCR, as well as their impact on renal function and histomorphology. RESULTS Intra-arterially injected Lin(-)CD90(+) HSCs were detected in the kidney at significant amounts only within the first 24 h after injection and were virtually absent by Day 2. Compared with control animals, no differences were seen after HSC administration with respect to kidney function or histomorphologic changes of AKI. At Day 7 HSCs were again readily detectable in the kidney suggesting a redistribution of cells at later time points. Of note, HSCs did not seem to have an exclusive tropism for the injured kidney but were detectable in the lungs, liver, spleen, heart and brain at all time points. CONCLUSIONS Injected HSCs do not appear to significantly contribute to tubular repair or ameliorate renal damage in ischaemic AKI although they may show considerable engraftment in various organs. These data further challenge the concept that injection of HSCs may be used as a therapeutic approach in treating AKI.
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Affiliation(s)
- Volker Burst
- Department II of Internal Medicine and Center for Molecular Medicine Cologne, University of Cologne, Cologne, Germany.
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Agostinelli C, Paterson JC, Gupta R, Righi S, Sandri F, Piccaluga PP, Bacci F, Sabattini E, Pileri SA, Marafioti T. Detection of LIM domain only 2 (LMO2) in normal human tissues and haematopoietic and non-haematopoietic tumours using a newly developed rabbit monoclonal antibody. Histopathology 2012; 61:33-46. [PMID: 22394247 DOI: 10.1111/j.1365-2559.2012.04198.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
AIMS We describe a new rabbit monoclonal antibody, raised against a fixation-resistant epitope of the transcription regulator LIM domain only 2 (LMO2). METHODS AND RESULTS Lymphoma cell lines and a large series of normal and neoplastic samples were investigated by Western blot and immunohistochemistry. The antibody detected nuclear positivity for the protein, with the exception of a proportion of classical Hodgkin lymphomas (HLs), peripheral T cell lymphomas (PTCLs) and solid tumours that showed granular cytoplasmic staining. In normal lympho-haematopoietic tissues, LMO2 was expressed at different intensities by CD34(+) blasts, haematopoietic precursors, germinal centre (GC), mantle and splenic marginal zone B cells. While reactive with only scattered elements in the thymus and nine of 237 PTCLs, the antibody stained 31 of 39 T-acute lymphoblastic lymphoma/leukaemias (T-ALLs) and the T-ALL-derived human leukaemic cell line, CCRF-CEM. LMO2 was found in 88% of B-acute lymphoblastic lymphoma/leukaemias (B-ALLs), 5% chronic lymphocytic leukaemias (CLLs) and 14%, 57% and 41% of mantle, follicular and Burkitt lymphomas, respectively. In the setting of diffuse large B cell lymphomas (DLBCLs), LMO2-positivity was related strongly to a GC phenotype. LMO2 was found in 83% primary mediastinal large B cell lymphomas (PMBLs) and 100% nodular lymphocyte predominant Hodgkin lymphomas (NLPHLs), whereas only 10% of classical HLs were stained. Acute and chronic myeloid leukaemias were usually positive. CONCLUSIONS The new anti-LMO2 antibody can be applied confidently to routine sections, contributing to the differential diagnosis of several lymphoma subtypes, subtyping of DLBCLs and potential development of innovative therapies.
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Affiliation(s)
- Claudio Agostinelli
- Section of Haematopathology, Department of Haematology and Oncological Sciences Seràgnoli, S Orsola-Malpighi Hospital, University of Bologna, Bologna, Italy.
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Bronstein R, Segal D. Modularity of CHIP/LDB transcription complexes regulates cell differentiation. Fly (Austin) 2011; 5:200-5. [PMID: 21406967 DOI: 10.4161/fly.5.3.14854] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Transcription is the first step through which the cell operates, via its repertoire of transcription complexes, to direct cellular functions and cellular identity by generating the cell-specific transcriptome. The modularity of the composition of constituents of these complexes allows the cell to delicately regulate its transcriptome. In a recent study we have examined the effects of reducing the levels of specific transcription co-factors on the function of two competing transcription complexes, namely CHIP-AP and CHIP-PNR which regulate development of cells in the thorax of Drosophila. We found that changing the availability of these co-factors can shift the balance between these complexes leading to transition from utilization of CHIP-AP to CHIP-PNR. This is reflected in change in the expression profile of target genes, altering developmental cell fates. We propose that such a mechanism may operate in normal fly development. Transcription complexes analogous to CHIP-AP and CHIP-PNR exist in mammals and we discuss how such a shift in the balance between them may operate in normal mammalian development.
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Affiliation(s)
- Revital Bronstein
- Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Tel Aviv, Israel
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Farrell JJ, Sherva RM, Chen ZY, Luo HY, Chu BF, Ha SY, Li CK, Lee ACW, Li RCH, Li CK, Yuen HL, So JCC, Ma ESK, Chan LC, Chan V, Sebastiani P, Farrer LA, Baldwin CT, Steinberg MH, Chui DHK. A 3-bp deletion in the HBS1L-MYB intergenic region on chromosome 6q23 is associated with HbF expression. Blood 2011; 117:4935-45. [PMID: 21385855 PMCID: PMC3100700 DOI: 10.1182/blood-2010-11-317081] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Fetal hemoglobin (HbF) is regulated as a multigenic trait. By genome-wide association study, we confirmed that HBS1L-MYB intergenic polymorphisms (HMIP) and BCL11A polymorphisms are highly associated with HbF in Chinese β-thalassemia heterozygotes. In this population, the variance in HbF resulting from the HMIP is 13.5%; that resulting from the BCL11A polymorphism is 6.4%. To identify the functional variant in HMIP, we used 1000 Genomes Project data, single nucleotide polymorphism imputation, comparisons of association results across populations, potential transcription factor binding sites, and analysis of phylogenetic conservation. Based on these studies, a hitherto unreported association between HbF expression and a 3-bp deletion, between 135 460 326 and 135 460 328 bp on chromosome 6q23 was found. This 3-bp deletion is in complete linkage disequilibrium with rs9399137, which is the single nucleotide polymorphism in HMIP most significantly associated with HbF among Chinese, Europeans, and Africans. Chromatin immunoprecipitation assays confirmed erythropoiesis-related transcription factors binding to this region in K562 cells. Based on transient expression of a luciferase reporter plasmid, the DNA fragment encompassing the 3-bp deletion polymorphism has enhancer-like activity that is further augmented by the introduction of the 3-bp deletion. This 3-bp deletion polymorphism is probably the most significant functional motif accounting for HMIP modulation of HbF in all 3 populations.
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Affiliation(s)
- John J Farrell
- Department of Medicine, Boston University School of Medicine, Boston, MA, USA
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Ruifrok WPT, Qian C, Silljé HHW, van Goor H, van Veldhuisen DJ, van Gilst WH, de Boer RA. Heart failure-associated anemia: bone marrow dysfunction and response to erythropoietin. J Mol Med (Berl) 2010; 89:377-87. [PMID: 21191566 PMCID: PMC3056002 DOI: 10.1007/s00109-010-0710-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2010] [Revised: 11/09/2010] [Accepted: 12/07/2010] [Indexed: 12/11/2022]
Abstract
Heart failure (HF)-associated anemia is common and has a poor outcome. Because bone marrow (BM) dysfunction may contribute to HF-associated anemia, we first investigated mechanisms of BM dysfunction in an established model of HF, the transgenic REN2 rat, which is characterized by severe hypertrophy and ventricular dilatation and SD rats as controls. Secondly, we investigated whether stimulation of hematopoiesis with erythropoietin (EPO) could restore anemia and BM dysfunction. After sacrifice, erythropoietic precursors (BFU-E) were isolated from the BM and cultured for 10 days. BFU-E were quantified and transcript abundance of genes involved in erythropoiesis were assayed. Number of BFU-E were severely decreased in BM of REN2 rats compared to SD rats (50 ± 6.2 vs. 6.4 ± 1.7, p < 0.01). EPO treatment increased hematocrit in the SD-EPO group (after 6 weeks, 49 ± 1 vs. 58 ± 1%, p < 0.01); however, in the mildly anemic REN2 rats, there was no effect (43 ± 1 vs. 44 ± 1%). This was paralleled by a 67% decrease in BFU-E in BM of REN2 rats compared to SD (p < 0.01). EPO significantly improved BFU-E in both SD and REN2 but could not restore this to control levels in the REN2 rats. Expression of several genes involved in differentiation (LMO2), mobilization (SDF-1), and iron incorporation (transferrin receptor) of the BM were differentially expressed in REN2 rats compared to SD rats, and EPO did not normalize this. Altogether, these results suggest that BM dysfunction is an important contributor to HF-associated anemia and that EPO is not an effective agent to treat HF-associated anemia.
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Affiliation(s)
- Willem-Peter T Ruifrok
- Department of Cardiology, University Medical Center Groningen, University of Groningen, Hanzeplein 1, 9713 GZ Groningen, The Netherlands
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Tian Y, Wang N, Lu Z. Repression of Lim only protein 4-activated transcription inhibits proliferation and induces apoptosis of normal mammary epithelial cells and breast cancer cells. Clin Exp Metastasis 2010; 27:455-63. [PMID: 20526802 DOI: 10.1007/s10585-010-9332-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Accepted: 04/30/2010] [Indexed: 12/18/2022]
Abstract
Lim only protein (LMO) 4 acts as a transcriptional adapter and modulates mammary gland morphogenesis as well as breast oncogenesis in transgenic mice. Yet, the molecular and cellular mechanisms of these effects remain to be fully elucidated. Engrailed LMO4 fusion protein is a powerful dominant repressor of LMO4 activated transcription that was successfully used to discover the role of LMO4 as a transcriptional activator in mammary gland development in our previous studies using mouse models. In this manuscript, we investigated the cellular effects of LMO4 in human normal mammary epithelial cells (HMECs) and breast cancer cell lines using the Engrailed-LMO4 fusion protein. HMEC cell growth was inhibited by the expression of the Engrailed-LMO4 fusion protein. The decrease in cell number was due to both decreased cell proliferation and enhanced apoptosis, suggesting that LMO4 promotes proliferation and survival of normal mammary epithelial cells. The expression of the Engrailed-LMO4 fusion protein also suppressed cell growth, and induced apoptosis in two breast cancer cell lines, MDA-MB-231 and T47D, suggesting that LMO4 contributes to oncogenesis by similar mechanisms of enhanced cell survival and proliferation. Taken together, our data indicate that LMO4 has similar cellular effects in normal mammary epithelial cells and breast cancer cells, and also provide direct evidence for the idea that normal development and carcinogenesis share conserved molecular mechanisms.
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Affiliation(s)
- Yingpu Tian
- Institute for Biomedical Research, Xiamen University, Fujian, China
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Zweier-Renn LA, Hawley TS, Burkett S, Ramezani A, Riz I, Adler RL, Hickstein DD, Hawley RG. Hematopoietic immortalizing function of the NKL-subclass homeobox gene TLX1. Genes Chromosomes Cancer 2010; 49:119-31. [PMID: 19862821 DOI: 10.1002/gcc.20725] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Translocations resulting in ectopic expression of the TLX1 homeobox gene (previously known as HOX11) are recurrent events in human T-cell acute lymphoblastic leukemia (T-ALL). Transduction of primary murine hematopoietic stem/progenitor cells with retroviral vectors expressing TLX1 readily yields immortalized hematopoietic progenitor cell lines. Understanding the processes involved in TLX1-mediated cellular immortalization should yield insights into the growth and differentiation pathways altered by TLX1 during the development of T-ALL. In recent clinical gene therapy trials, hematopoietic clonal dominance or T-ALL-like diseases have occurred as a direct consequence of insertional activation of the EVI1, PRDM16 or LMO2 proto-oncogenes by the retroviral vectors used to deliver the therapeutic genes. Additionally, the generation of murine hematopoietic progenitor cell lines due to retroviral integrations into Evi1 or Prdm16 has also been recently reported. Here, we determined by linker-mediated nested polymerase chain reaction the integration sites in eight TLX1-immortalized hematopoietic cell lines. Notably, no common integration site was observed among the cell lines. Moreover, no insertions into the Evi1 or Prdm16 genes were identified although insertion near Lmo2 was observed in one instance. However, neither Lmo2 nor any of the other genes examined surrounding the integration sites showed differential vector-influenced expression compared to the cell lines lacking such insertions. While we cannot exclude the possibility that insertional side effects transiently provided a selective growth/survival advantage to the hematopoietic progenitor populations, our results unequivocally rule out insertions into Evi1 and Prdm16 as being integral to the TLX1-initiated immortalization process.
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Affiliation(s)
- Lynnsey A Zweier-Renn
- Department of Anatomy and Regenerative Biology, The George Washington University, Washington, DC 20037, USA
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Yang M, Qian XH, Zhao DH, Fu SZ. Effects of Astragalus polysaccharide on the erythroid lineage and microarray analysis in K562 cells. JOURNAL OF ETHNOPHARMACOLOGY 2010; 127:242-250. [PMID: 19922785 DOI: 10.1016/j.jep.2009.11.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 10/30/2009] [Accepted: 11/08/2009] [Indexed: 05/26/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Astragalus polysaccharide (APS), obtained from Astragalus membranaceus, displays a range of activities in many systems, including the promotion of immune responses, anti-inflammation, and the protection of vessels. It possesses potent pharmacological activity on differentiation to the erythroid lineage. AIM OF THE STUDY To investigate the effects of APS on the erythroid differentiation and the mechanism of action by microarray analysis in K562 cells. MATERIALS AND METHODS Benzidine staining, semi-quantitative RT-PCR, Western blot and microarray methods were used to survey the effects of APS on inducing erythroid differentiation and the changes of gene expression profile in K562 cells. RESULTS Of the 13.2% positive cells detected by benzidine staining, the induction was the highest with 200 microg/ml APS on 72h. Ggamma-mRNA expression and fetal hemoglobin synthesis were significantly up-regulated. Microarray analysis showed that 31 genes were up-regulated and 108 genes were down-regulated. These differential expression genes generally regulate protein binding, cellular metabolic process, the cell proliferation, and transcriptional activator activity. The gamma-globin gene was up-regulated, the genes related with erythroid differentiation such as LMO2, Runx1 and GTF2I were up-regulated, while Bklf, Eklf, EPHB4 and Sp1 were down-regulated. CONCLUSIONS Our studies indicate that APS indicate potent activities on the erythroid differentiation by modulating genes of LMO2, Klf1, Klf3, Runx1, EphB4 and Sp1, increasing gamma-globin mRNA expression and fetal hemoglobin synthesis in K562 cells.
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Affiliation(s)
- Min Yang
- Department of Neonatology, Nanfang Hospital Affiliated Nanfang Medical University, 1838 Guang Zhou Da Dao North, Guangzhou 510515, Guangdong, PR China
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Felli N, Pedini F, Romania P, Biffoni M, Morsilli O, Castelli G, Santoro S, Chicarella S, Sorrentino A, Peschle C, Marziali G. MicroRNA 223-dependent expression of LMO2 regulates normal erythropoiesis. Haematologica 2009; 94:479-86. [PMID: 19278969 DOI: 10.3324/haematol.2008.002345] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND MicroRNAs are small non-coding RNAs that regulate gene expression through mRNA degradation or translational inhibition. MicroRNAs are emerging as key regulators of normal hematopoiesis and hematologic malignancies. Several miRNAs are differentially expressed during hematopoiesis and their specific expression regulates key functional proteins involved in hematopoietic lineage differentiation. This study focused on the functional role of microRNA-223 (miR-223) on erythroid differentiation. DESIGN AND METHODS Purified cord blood CD34+ hematopoietic progenitor cells were grown in strictly controlled conditions in the presence of saturating dosage of erythropoietin to selectively induce erythroid differentiation. The effects of enforced expression of miR-223 in unilin-eage erythroid cultures were evaluated in liquid phase culture experiments and clonogenic studies. RESULTS In unilineage erythroid culture of cord blood CD34+ hematopoietic progenitor cells miR-223 is down-regulated, whereas LMO2, an essential protein for erythroid differentiation, is up-regulated. Functional studies showed that enforced expression of miR-223 reduces the mRNA and protein levels of LMO2, by binding to LMO2 3' UTR, and impairs differentiation of erythroid cells. Accordingly, knockdown of LMO2 by short interfering RNA mimics the action of miR-223. Furthermore, hematopoietic progenitor cells transduced with miR-223 showed a significant reduction of their erythroid clonogenic capacity, suggesting that downmodulation of this miRNA is required for erythroid progenitor recruitment and commitment. CONCLUSIONS These results show that the decline of miR-223 is an important event for erythroid differentiation that leads to the expansion of erythroblast cells at least partially mediated by unblocking LMO2 protein expression.
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Affiliation(s)
- Nadia Felli
- Dept. of Hematology, Oncology and Molecular Medicine, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
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Drosophila LIM-only is a positive regulator of transcription during thoracic bristle development. Genetics 2008; 179:1989-99. [PMID: 18689881 DOI: 10.1534/genetics.108.090076] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The Drosophila LIM-only (LMO) protein DLMO functions as a negative regulator of transcription during development of the fly wing. Here we report a novel role of DLMO as a positive regulator of transcription during the development of thoracic sensory bristles. We isolated new dlmo mutants, which lack some thoracic dorsocentral (DC) bristles. This phenotype is typical of malfunction of a thoracic multiprotein transcription complex, composed of CHIP, PANNIER (PNR), ACHAETE (AC), and DAUGHTERLESS (DA). Genetic interactions reveal that dlmo synergizes with pnr and ac to promote the development of thoracic DC bristles. Moreover, loss-of-function of dlmo reduces the expression of a reporter target gene of this complex in vivo. Using the GAL4-UAS system we also show that dlmo is spatially expressed where this complex is known to be active. Glutathione-S-transferase (GST)-pulldown assays showed that DLMO can physically bind CHIP and PNR through either of the two LIM domains of DLMO, suggesting that DLMO might function as part of this transcription complex in vivo. We propose that DLMO exerts its positive effect on DC bristle development by serving as a bridging molecule between components of the thoracic transcription complex.
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Frith MC, Saunders NFW, Kobe B, Bailey TL. Discovering sequence motifs with arbitrary insertions and deletions. PLoS Comput Biol 2008; 4:e1000071. [PMID: 18437229 PMCID: PMC2323616 DOI: 10.1371/journal.pcbi.1000071] [Citation(s) in RCA: 241] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2007] [Accepted: 03/27/2008] [Indexed: 01/14/2023] Open
Abstract
BIOLOGY IS ENCODED IN MOLECULAR SEQUENCES: deciphering this encoding remains a grand scientific challenge. Functional regions of DNA, RNA, and protein sequences often exhibit characteristic but subtle motifs; thus, computational discovery of motifs in sequences is a fundamental and much-studied problem. However, most current algorithms do not allow for insertions or deletions (indels) within motifs, and the few that do have other limitations. We present a method, GLAM2 (Gapped Local Alignment of Motifs), for discovering motifs allowing indels in a fully general manner, and a companion method GLAM2SCAN for searching sequence databases using such motifs. glam2 is a generalization of the gapless Gibbs sampling algorithm. It re-discovers variable-width protein motifs from the PROSITE database significantly more accurately than the alternative methods PRATT and SAM-T2K. Furthermore, it usefully refines protein motifs from the ELM database: in some cases, the refined motifs make orders of magnitude fewer overpredictions than the original ELM regular expressions. GLAM2 performs respectably on the BAliBASE multiple alignment benchmark, and may be superior to leading multiple alignment methods for "motif-like" alignments with N- and C-terminal extensions. Finally, we demonstrate the use of GLAM2 to discover protein kinase substrate motifs and a gapped DNA motif for the LIM-only transcriptional regulatory complex: using GLAM2SCAN, we identify promising targets for the latter. GLAM2 is especially promising for short protein motifs, and it should improve our ability to identify the protein cleavage sites, interaction sites, post-translational modification attachment sites, etc., that underlie much of biology. It may be equally useful for arbitrarily gapped motifs in DNA and RNA, although fewer examples of such motifs are known at present. GLAM2 is public domain software, available for download at http://bioinformatics.org.au/glam2.
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Affiliation(s)
- Martin C Frith
- Computational Biology Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Tokyo, Japan.
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