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Jiao B, Taniguchi-Ishigaki N, Güngör C, Peters MA, Chen YW, Riethdorf S, Drung A, Ahronian LG, Shin J, Pagnis R, Pantel K, Tachibana T, Lewis BC, Johnsen SA, Bach I. Functional activity of RLIM/Rnf12 is regulated by phosphorylation-dependent nucleocytoplasmic shuttling. Mol Biol Cell 2013; 24:3085-96. [PMID: 23904271 PMCID: PMC3784382 DOI: 10.1091/mbc.e13-05-0239] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
In mice, the ubiquitin ligase RLIM/Rnf12 is a critical survival factor for mammary milk-producing alveolar cells, but little is known about how its activity is regulated. It is shown here that RLIM shuttles between the nucleus and cytoplasm in a phosphorylation-dependent manner, and shuttling is important for its alveolar survival function. The X-linked gene Rnf12 encodes the ubiquitin ligase really interesting new gene (RING) finger LIM domain–interacting protein (RLIM)/RING finger protein 12 (Rnf12), which serves as a major sex-specific epigenetic regulator of female mouse nurturing tissues. Early during embryogenesis, RLIM/Rnf12 expressed from the maternal allele is crucial for the development of extraembryonic trophoblast cells. In contrast, in mammary glands of pregnant and lactating adult females RLIM/Rnf12 expressed from the paternal allele functions as a critical survival factor for milk-producing alveolar cells. Although RLIM/Rnf12 is detected mostly in the nucleus, little is known about how and in which cellular compartment(s) RLIM/Rnf12 mediates its biological functions. Here we demonstrate that RLIM/Rnf12 protein shuttles between nucleus and cytoplasm and this is regulated by phosphorylation of serine S214 located within its nuclear localization sequence. We show that shuttling is important for RLIM to exert its biological functions, as alveolar cell survival activity is inhibited in cells expressing shuttling-deficient nuclear or cytoplasmic RLIM/Rnf12. Thus regulated nucleocytoplasmic shuttling of RLIM/Rnf12 coordinates cellular compartments during mammary alveolar cell survival.
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Affiliation(s)
- Baowei Jiao
- Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA 01605-2324 Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605-2324 Centre for Molecular Neurobiology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany Institute for Tumor Biology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
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Jiao B, Ma H, Shokhirev MN, Drung A, Yang Q, Shin J, Lu S, Byron M, Kalantry S, Mercurio AM, Lawrence JB, Hoffmann A, Bach I. Paternal RLIM/Rnf12 is a survival factor for milk-producing alveolar cells. Cell 2012; 149:630-41. [PMID: 22541433 DOI: 10.1016/j.cell.2012.02.056] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Revised: 12/12/2011] [Accepted: 02/21/2012] [Indexed: 11/18/2022]
Abstract
In female mouse embryos, somatic cells undergo a random form of X chromosome inactivation (XCI), whereas extraembryonic trophoblast cells in the placenta undergo imprinted XCI, silencing exclusively the paternal X chromosome. Initiation of imprinted XCI requires a functional maternal allele of the X-linked gene Rnf12, which encodes the ubiquitin ligase Rnf12/RLIM. We find that knockout (KO) of Rnf12 in female mammary glands inhibits alveolar differentiation and milk production upon pregnancy, with alveolar cells that lack RLIM undergoing apoptosis as they begin to differentiate. Genetic analyses demonstrate that these functions are mediated primarily by the paternal Rnf12 allele due to nonrandom maternal XCI in mammary epithelial cells. These results identify paternal Rnf12/RLIM as a critical survival factor for milk-producing alveolar cells and, together with population models, reveal implications of transgenerational epigenetic inheritance.
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Affiliation(s)
- Baowei Jiao
- Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA 01605, USA
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Güngör C, Taniguchi-Ishigaki N, Ma H, Drung A, Tursun B, Ostendorff HP, Bossenz M, Becker CG, Becker T, Bach I. Proteasomal selection of multiprotein complexes recruited by LIM homeodomain transcription factors. Proc Natl Acad Sci U S A 2007; 104:15000-5. [PMID: 17848518 PMCID: PMC1986602 DOI: 10.1073/pnas.0703738104] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Complexes composed of multiple proteins regulate most cellular functions. However, our knowledge about the molecular mechanisms governing the assembly and dynamics of these complexes in cells remains limited. The in vivo activity of LIM homeodomain (LIM-HD) proteins, a class of transcription factors that regulates neuronal development, depends on the high-affinity association of their LIM domains with cofactor of LIM homeodomain proteins (LIM-HDs) (CLIM, also known as Ldb or NLI). CLIM cofactors recruit single-stranded DNA-binding protein 1 (SSDP1, also known as SSBP3), and this interaction is important for the activation of the LIM-HD/CLIM protein complex in vivo. Here, we identify a cascade of specific protein interactions that protect LIM-HD multiprotein complexes from proteasomal degradation. In this cascade, CLIM stabilizes LIM-HDs, and SSDP1 stabilizes CLIM. Furthermore, we show that stabilizing cofactors prevent binding of ubiquitin ligases to multiple protein interaction domains in LIM-HD recruited protein complexes. Together, our results indicate a combinatorial code that selects specific multiprotein complexes via proteasomal degradation in cells with broad implications for the assembly and specificity of multiprotein complexes.
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Affiliation(s)
| | | | - Hong Ma
- Programs in *Gene Function and Expression and
| | | | | | - Heather P. Ostendorff
- Center for Molecular Neurobiology (ZMNH), University of Hamburg, D-20251 Hamburg, Germany; and
| | - Michael Bossenz
- Center for Molecular Neurobiology (ZMNH), University of Hamburg, D-20251 Hamburg, Germany; and
| | - Catherina G. Becker
- Centre for Neuroscience Research, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Summerhall, Edinburgh EH9 1QH, United Kingdom
| | - Thomas Becker
- Centre for Neuroscience Research, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Summerhall, Edinburgh EH9 1QH, United Kingdom
| | - Ingolf Bach
- Programs in *Gene Function and Expression and
- Molecular Medicine, University of Massachusetts Medical School, Worcester, MA 01605
- **To whom correspondence should be addressed. E-mail:
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Ostendorff HP, Tursun B, Cornils K, Schlüter A, Drung A, Güngör C, Bach I. Dynamic expression of LIM cofactors in the developing mouse neural tube. Dev Dyn 2006; 235:786-91. [PMID: 16395690 DOI: 10.1002/dvdy.20669] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The developmental regulation of LIM homeodomain transcription factors (LIM-HD) by the LIM domain-binding cofactors CLIM/Ldb/NLI and RLIM has been demonstrated. Whereas CLIM cofactors are thought to be required for at least some of the in vivo functions of LIM-HD proteins, the ubiquitin ligase RLIM functions as a negative regulator by its ability to target CLIM cofactors for proteasomal degradation. In this report, we have investigated and compared the protein expression of both factors in the developing mouse neural tube. We co-localize both proteins in many tissues and, although widely expressed, we detect high levels of both cofactors in specific neural tube regions, e.g., in the ventral neural tube, where motor neurons reside. The mostly ubiquitous distribution of RLIM- and CLIM-encoding mRNA differs from the more specific expression of both cofactors at the protein level, indicating post-transcriptional regulation. Furthermore, we show that both cofactors not only co-localize with each other but also with Isl and Lhx3 LIM-HD proteins in developing ventral neural tube neurons. Our results demonstrate the dynamic expression of cofactors participating in the regulation of LIM-HD proteins during the development of the neural tube in mice and suggest additional post-transcriptional regulation in the nuclear LIM-HD protein network.
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Affiliation(s)
- Heather P Ostendorff
- Zentrum für Molekulare Neurobiologie Hamburg , Universität Hamburg, Martinistr. 85, 20251 Hamburg, Germany
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Tursun B, Schlüter A, Peters MA, Viehweger B, Ostendorff HP, Soosairajah J, Drung A, Bossenz M, Johnsen SA, Schweizer M, Bernard O, Bach I. The ubiquitin ligase Rnf6 regulates local LIM kinase 1 levels in axonal growth cones. Genes Dev 2005; 19:2307-19. [PMID: 16204183 PMCID: PMC1240040 DOI: 10.1101/gad.1340605] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2005] [Accepted: 08/10/2005] [Indexed: 11/25/2022]
Abstract
LIM kinase 1 (LIMK1) controls important cellular functions such as morphogenesis, cell motility, tumor cell metastasis, development of neuronal projections, and growth cone actin dynamics. We have investigated the role of the RING finger protein Rnf6 during neuronal development and detected high Rnf6 protein levels in developing axonal projections of motor and DRG neurons during mouse embryogenesis as well as cultured hippocampal neurons. RNAi-mediated knock-down experiments in primary hippocampal neurons identified Rnf6 as a regulator of axon outgrowth. Consistent with a role in axonal growth, we found that Rnf6 binds to, polyubiquitinates, and targets LIMK1 for proteasomal degradation in growth cones of primary hippocampal neurons. Rnf6 is functionally linked to LIMK1 during the development of axons, as the changes in axon outgrowth induced by up- or down-regulation of Rnf6 levels can be restored by modulation of LIMK1 expression. Thus, these results assign a specific role for Rnf6 in the control of cellular LIMK1 concentrations and indicate a new function for the ubiquitin/proteasome system in regulating local growth cone actin dynamics.
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Affiliation(s)
- Baris Tursun
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, 20251 Hamburg, Germany
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Piekielko A, Drung A, Rogalla P, Schwanbeck R, Heyduk T, Gerharz M, Bullerdiek J, Wiśniewski JR. Distinct organization of DNA complexes of various HMGI/Y family proteins and their modulation upon mitotic phosphorylation. J Biol Chem 2001; 276:1984-92. [PMID: 11034995 DOI: 10.1074/jbc.m004065200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
High mobility group (HMG) proteins HMGI, HMGY, HMGI-C, and Chironomus HMGI are DNA-binding proteins thought to modulate the assembly and the function of transcriptional complexes. Each of these proteins contains three DNA-binding domains (DBD), properties of which appear to be regulated by phosphorylation. High levels of these proteins are characteristic for rapidly dividing cells in embryonic tissues and tumors. On the basis of their occurrence, specific functions for each of these proteins have been postulated. In this study we demonstrate differences in the nature of contacts of these proteins with promoter region of the interferon-beta gene. We show that HMGI and HMGY interact with this DNA via three DBDs, whereas HMGI-C and Chironomus HMGI bind to this DNA using only two domains. Phosphorylation of HMGY protein by Cdc2 kinase leads to impairing of contacts between the N-terminally located DBD and a single promoter element. The perturbations in the architecture of the protein.DNA complexes involve changes in the degree of unbending of the intrinsically bent IFNbeta promoter. Our results provide first insights into the molecular basis of functional specificity of proteins of the HMGI/Y family and their regulation by phosphorylation.
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Affiliation(s)
- A Piekielko
- III. Zoologisches Institut-Entwicklungsbiologie, Universität Göttingen, D-37073 Göttingen, Germany
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Schwanbeck R, Gerharz M, Drung A, Rogalla P, Piekielko A, Blank C, Bullerdiek J, Wiśniewski JR. Point mutations within AT-hook domains of the HMGI homologue HMGIYL1 affect binding to gene promoter but not to four-way junction DNA. Biochemistry 2000; 39:14419-25. [PMID: 11087394 DOI: 10.1021/bi0011274] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
High-mobility group I/Y (HMGI/Y) proteins are chromosomal proteins involved in gene and chromatin regulation. Elevated levels of HMGI/Y proteins were reported in diverse malignant tumors, and rearrangements of their genes are casually involved in the development of benign tumors. In humans, the chromosomal locus Xp22 has been often found to be affected in diverse benign mesenchymal tumors. Recent studies revealed that this region contains a retropseudogene HMGIYL1 which potentially can be activated in a way of "exonization" upon aberrations involving this region. The coding sequence of the HMGIY-L1 is highly homologous to the HMGI(Y) gene. On the protein level, both HMGIYL1 and HMGI differ at few amino acid residues, including their putative DNA-binding domains (DBDs). Here we have approached the question of whether the HMGIYL1 product would be able to adopt a role of HMGI in the context of binding to gene promoters and chromatin. Comparative binding studies, employing protein footprinting technique, revealed that HMGIYL1 has lost the ability to bind to the promoter of the interferon beta gene, but retained its high affinity for the four-way junction DNA. Our results stress the importance of particular residues within the DBDs for DNA binding and demonstrate that tight binding of HMGI/Y proteins to the four-way junction DNA can be achieved in alternative ways. The binding of HMGIYL1 to four-way junction DNA suggests that activation of the HMGIYL1 gene would yield a protein sharing some binding properties with HMG1-box proteins and histone H1. Thus, the HMGIYL1 could interplay together with these components in chromatin regulation.
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Affiliation(s)
- R Schwanbeck
- Zoologisches Institut-Entwicklungsbiologie, Universität Göttingen, D-37073 Göttingen, Germany
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