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1.
Int J Mol Sci ; 22(19)2021 Sep 29.
Artículo en Inglés | MEDLINE | ID: mdl-34638866

RESUMEN

RBM10 is an RNA-binding protein that regulates alternative splicing (AS). It localizes to the extra-nucleolar nucleoplasm and S1-1 nuclear bodies (NBs) in the nucleus. We investigated the biological significance of this localization in relation to its molecular function. Our analyses, employing deletion mutants, revealed that RBM10 possesses two S1-1 NB-targeting sequences (NBTSs), one in the KEKE motif region and another in the C2H2 Zn finger (ZnF). These NBTSs act synergistically to localize RBM10 to S1-1 NBs. The C2H2 ZnF not only acts as an NBTS, but is also essential for AS regulation by RBM10. Moreover, RBM10 does not participate in S1-1 NB formation, and without alterations of RBM10 protein levels, its NB-localization changes, increasing as cellular transcriptional activity declines, and vice versa. These results indicate that RBM10 is a transient component of S1-1 NBs and is sequestered in NBs via its NBTSs when cellular transcription decreases. We propose that the C2H2 ZnF exerts its NB-targeting activity when RBM10 is unbound by pre-mRNAs, and that NB-localization of RBM10 is a mechanism to control its AS activity in the nucleus.


Asunto(s)
Empalme Alternativo , Núcleo Celular/metabolismo , Señales de Localización Nuclear/metabolismo , Proteínas de Unión al ARN/metabolismo , Secuencias de Aminoácidos , Núcleo Celular/genética , Células HEK293 , Células HeLa , Células Hep G2 , Humanos , Señales de Localización Nuclear/genética , Dominios Proteicos , Transporte de Proteínas , Proteínas de Unión al ARN/genética
2.
Genes Cells ; 25(2): 100-110, 2020 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-31820547

RESUMEN

RNA-binding motif protein 10 (RBM10) primarily regulates alternative splicing of certain genes. Loss-of-function mutations in RBM10 have been frequently reported in patients with various cancers. However, how RBM10 levels affect cell proliferation and tumorigenesis remains unknown. To elucidate the role of RBM10 in cell proliferation, we established HepG2-RBM10 knockout cell lines and derivative doxycycline-inducible RBM10-expressing cells. RBM10 over-expression caused growth arrest in the M phase with a monopolar spindle because of impaired centriole duplication. Two RBM10 splicing mutants, one with F345A/F347A and the other with only the C-terminal half (401-930), were sufficient to cause growth arrest, whereas an RBM10 mutant with cytoplasmic localization forced by an NES did not show growth arrest. RBM10 over-expression induced the formation of many large nuclear domains containing RBM10, PLK4, STIL and SAS6, which are the regulatory proteins involved in centriole duplication. Consistently, the centrioles in the RBM10-over-expressing HepG2 cells lost PLK4 and STIL, accounting for the unsuccessful centriole duplication. In contrast, RBM10 depletion resulted in elevated levels of cytoplasmic PLK4 with a concomitant increase in the number of centrioles in HepG2 cells but not in A549 cells. Thus, nuclear RBM10 regulates normal chromosomal division in a cell-type-specific manner, independent of alternative RNA splicing.


Asunto(s)
Núcleo Celular/metabolismo , Centriolos/metabolismo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Carcinogénesis/genética , Ciclo Celular/genética , Ciclo Celular/fisiología , Proteínas de Ciclo Celular/metabolismo , Proliferación Celular , Regulación de la Expresión Génica , Técnicas de Inactivación de Genes , Células Hep G2 , Humanos , Transcriptoma
3.
PLoS One ; 14(8): e0217605, 2019.
Artículo en Inglés | MEDLINE | ID: mdl-31404068

RESUMEN

Telomerase is a ribonucleoprotein ribonucleic enzyme that is essential for cellular immortalization via elongation of telomere repeat sequences at the end of chromosomes. Human telomerase reverse transcriptase (hTERT), the catalytic subunit of telomerase holoenzyme, is a key regulator of telomerase activity. Telomerase activity, which has been detected in the majority of cancer cells, is accompanied by hTERT expression, suggesting that this enzyme activity contributes to an unlimited replication potential of cancer cells via regulation of telomere length. Thus, hTERT is an attractive target for cancer-specific treatments. We previously reported that pared-like homeodomain 1 (PITX1) is a negative regulator of hTERT through direct binding to the hTERT promoter. However, the mechanism by which the function of PITX1 contributes to transcriptional silencing of the hTERT gene remains to be clarified. Here, we show that PITX1 and zinc finger CCHC-type containing 10 (ZCCHC10) proteins cooperate to facilitate the transcriptional regulation of the hTERT gene by functional studies via FLAG pull-down assay. Co-expression of PITX1 and ZCCHC10 resulted in inhibition of hTERT transcription, in melanoma cell lines, whereas mutate-deletion of homeodomain in PITX1 that interact with ZCCHC10 did not induce similar phenotypes. In addition, ZCCHC10 expression levels showed marked decrease in the majority of melanoma cell lines and tissues. Taken together, these results suggest that ZCCHC10-PITX1 complex is the functional unit that suppresses hTERT transcription, and may play a crucial role as a novel tumor suppressor complex.


Asunto(s)
Regulación Enzimológica de la Expresión Génica , Melanoma/metabolismo , Factores de Transcripción Paired Box/metabolismo , ARN Mensajero/metabolismo , Telomerasa/metabolismo , Factores de Transcripción/metabolismo , Dedos de Zinc/genética , Humanos , Melanoma/genética , Factores de Transcripción Paired Box/genética , Regiones Promotoras Genéticas , Dominios y Motivos de Interacción de Proteínas , ARN Mensajero/genética , Telomerasa/genética , Factores de Transcripción/genética , Transcripción Genética , Células Tumorales Cultivadas
4.
Biochem Biophys Res Commun ; 453(3): 588-94, 2014 Oct 24.
Artículo en Inglés | MEDLINE | ID: mdl-25285631

RESUMEN

Mitotic catastrophe, a form of cell death that occurs during mitosis and after mitotic slippage to a tetraploid state, plays an important role in the efficacy of cancer cell killing by microtubule inhibitors. Prolonged mitotic arrest at the spindle assembly checkpoint (SAC) is a well-known requirement for mitotic catastrophe and, thus, for conferring sensitivity to microtubule inhibitors. We previously reported that downregulation of SIRT2, a member of the sirtuin family of NAD+-dependent deacetylases, confers resistance to microtubule inhibitors by abnormally prolonging mitotic arrest and thus compromising the cell death pathway after mitotic slippage. Thus, turning off SAC activation after a defined period is an additional requirement for efficient post-slippage death. Here, we investigated whether SIRT2 deacetylates BubR1, which is a core component of the SAC; acetylation of BubR1 at lysine 250 (K250) during prometaphase inhibits its APC/C-dependent proteolysis and thus regulates timing in anaphase entry. We showed that SIRT2 deacetylates BubR1 K250 both in vitro and in vivo. We also found that SIRT2 knockdown leads to increased levels of BubR1 acetylation at prometaphase; however, this increase is not substantial to elevate the levels of total BubR1 or delay the transition from prometaphase to anaphase. The present study shows that SIRT2 is a deacetylase for BubR1 K250, although the abnormally prolonged SAC activation observed in SIRT2 knockdown cells is not accompanied by a change in BubR1 levels or by delayed progression from prometaphase to anaphase.


Asunto(s)
Anafase , Prometafase , Proteínas Serina-Treonina Quinasas/metabolismo , Sirtuina 2/metabolismo , Acetilación , Línea Celular , Técnicas de Silenciamiento del Gen , Humanos , Proteínas Serina-Treonina Quinasas/química , Proteolisis , Sirtuina 2/química , Sirtuina 2/genética
5.
FEBS J ; 281(11): 2623-37, 2014 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-24712640

RESUMEN

Mitotic catastrophe, a form of cell death that occurs during mitosis and after mitotic slippage to a tetraploid state, plays important roles in the efficacy of cancer cell killing by microtubule inhibitors (MTIs). Prolonged mitotic arrest by the spindle assembly checkpoint is a well-known requirement for mitotic catastrophe, and thus for conferring sensitivity to MTIs. We previously reported that turning off spindle assembly checkpoint activation after a defined period of time is another requirement for efficient postslippage death from a tetraploid state, and we identified SIRT2, a member of the sirtuin protein family, as a regulator of this process. Here, we investigated whether SIRT2 regulates basal autophagy and whether, in that case, autophagy regulation by SIRT2 is required for postslippage death, by analogy with previous insights into SIRT1 functions in autophagy. We show, by combined knockdown of autophagy genes and SIRT2, that SIRT2 serves this function at least partially by suppressing basal autophagy levels. Notably, increased autophagy induced by rapamycin and mild starvation caused mitotic arrest for an abnormally long period of time in the presence of MTIs, and this was followed by delayed postslippage death, which was also observed in cells with SIRT2 knockdown. These results underscore a causal association among increased autophagy levels, mitotic arrest for an abnormally long period of time after exposure to MTIs, and resistance to MTIs. Although autophagy acts as a tumor suppressor mechanism, this study highlights its negative aspects, as increased autophagy may cause mitotic catastrophe malfunction. Thus, SIRT2 offers a novel target for tumor therapy.


Asunto(s)
Sirtuina 2/genética , Autofagia/efectos de los fármacos , Autofagia/genética , Células HCT116 , Humanos , Mitosis/efectos de los fármacos , Mitosis/genética , Sirtuina 1/deficiencia , Sirtuina 1/genética , Sirtuina 2/deficiencia , Huso Acromático/efectos de los fármacos , Huso Acromático/metabolismo , Moduladores de Tubulina/farmacología
6.
Biol Cell ; 105(4): 162-74, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23294349

RESUMEN

BACKGROUND INFORMATION: S1-1, also called RBM10, is an RNA-binding protein of 852 residues. An alteration of its activity causes TARP syndrome, a severe X-linked disorder with pre- or post-natal lethality in affected males. Its molecular function, although still largely unknown, has been suggested to be transcription and alternative splicing. In fact, S1-1 localises in the nucleus in tissue cells and cultured cells. RESULTS: By deletion and substitution mutagenesis, a classical 17-amino-acid (aa) nuclear localisation sequence (NLS1) was identified at aa 743-759 in the C-terminal region of S1-1. NLS1 was bipartite, with its N-terminal basic cluster weakly contributing to the NLS activity. S1-1 contained two additional NLSs. One was in the aa 60-136 RNA recognition motif region (NLS2), and the other was a novel NLS motif sequence in the aa 481-540 octamer-repeat (OCRE) region (NLS3). The OCRE is a domain known to be critical in splicing regulation, as shown with RBM5, a close homologue of RBM10 [Bonnal et al. (2008) Mol. Cell 32, 81-95]. The NLS activities were verified by expressing each DNA sequence linked to EGFP or a FLAG tag. These multiple NLSs acted cooperatively, and S1-1 became completely cytoplasmic after the concomitant removal of all NLS domains. In some cell types, however, S1-1 was partly cytoplasmic, suggesting that cellular localisation of S1-1 is subjected to regulation. CONCLUSIONS: The present results indicate that S1-1 contains multiple NLSs that act cooperatively. Among them, the OCRE is a hitherto unreported NLS. The nuclear localisation of S1-1 appears to be regulated under certain circumstances. We discuss these NLSs in relation to the biochemical processes they are involved in.


Asunto(s)
Núcleo Celular/metabolismo , Señales de Localización Nuclear , Proteínas de Unión al ARN/química , Proteínas de Unión al ARN/metabolismo , Secuencia de Aminoácidos , Núcleo Celular/genética , Humanos , Datos de Secuencia Molecular , Estructura Terciaria de Proteína , Transporte de Proteínas , Proteínas de Unión al ARN/genética
7.
JAKSTAT ; 2(4): e25763, 2013 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-24416650

RESUMEN

Cytokines play several roles in developing and/or reinforcing premature cellular senescence of young cells. One such cytokine, interleukin-6 (IL-6), regulates senescence in some systems in addition to its known functions of immune regulation and promotion of tumorigenesis. In this review, we describe recent advances in studies on the roles of IL-6 and its downstream signal transducer and activator of transcription 3 (STAT3) in regulating premature cellular senescence. IL-6/sIL-6Rα stimulation forms a senescence-inducing circuit involving the STAT3-insulin-like growth factor-binding protein 5 (IGFBP5) as a key axis triggering and reinforcing component in human fibroblasts. We describe how cytokines regulate the process of senescence by activating STAT3 in one system and anti-senescence or tumorigenesis in other systems. The roles of other STAT members in premature senescence also will be discussed to show the multiple mechanisms leading to cytokine-induced senescence.

8.
Cell Cycle ; 11(4): 730-9, 2012 Feb 15.
Artículo en Inglés | MEDLINE | ID: mdl-22374671

RESUMEN

Cells undergo senescence in response to various conditions, including telomere erosion, oncogene activation and multiple cytokines. One of these cytokines, interleukin-6 (IL­6), not only functions in the immune system, but also promotes cellular senescence and cancer. Here we demonstrate that IL­6 and the soluble IL­6 receptor (sIL­6R) induce premature senescence in normal human fibroblasts by establishing a senescence-inducing circuit involving the signal transducer and activator of transcription 3 (STAT3) and insulin-like growth factor-binding protein 5 (IGFBP5). Stimulating TIG3 fibroblast cells with IL­6/sIL­6R sequentially caused an increase in reactive oxygen species (ROS) as early as day 1, followed by the DNA damage response, p53 accumulation and, finally, senescence on days 8-10. We found that STAT3 was required for the events leading to senescence, including the initial early-phase ROS increase and the induction of IL­1α/ß, IL­6 and CXCL8 mRNAs 4-5 d after IL­6/sIL­6R stimulation, suggesting that STAT3's role is indirect. We searched for STAT3-downstream molecule(s) responsible for the senescence-inducing activity in the supernatants of stimulated TIG3 and identified IGFBP5 as a major STAT3 mediator, because IGFBP5 was expressed from the early phase through the entire senescence process and was responsible for IL­6/STAT3-induced ROS increase and premature senescence. Thus, IL­6/sIL­6R forms a senescence-inducing circuit involving the STAT3-IGFBP5 axis as a key triggering and reinforcing component.


Asunto(s)
Senescencia Celular/efectos de los fármacos , Receptor gp130 de Citocinas/farmacología , Fibroblastos/efectos de los fármacos , Fibroblastos/metabolismo , Proteína 5 de Unión a Factor de Crecimiento Similar a la Insulina/metabolismo , Interleucina-6/farmacología , Factor de Transcripción STAT3/metabolismo , Western Blotting , Línea Celular , Senescencia Celular/genética , Humanos , Proteína 5 de Unión a Factor de Crecimiento Similar a la Insulina/genética , Interferencia de ARN , Especies Reactivas de Oxígeno/metabolismo , Reacción en Cadena en Tiempo Real de la Polimerasa , Factor de Transcripción STAT3/genética
9.
Genes Cells ; 17(2): 132-45, 2012 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-22233524

RESUMEN

Signal transducer and activator of transcription 3 (STAT3) is a latent cytoplasmic transcription factor. It is activated by cytokines, including interleukin-6 (IL-6) through phosphorylation at Tyr705 (pY705), which is required for its dimerization and nuclear translocation. However, the role of Ser727 phosphorylation, occurring during activation, remains poorly understood. Using a combination of HepG2-stat3-knockdown cells reconstituted with various STAT3 mutants and protein kinase inhibitors, we showed that phospho-S727 has an intrinsic mechanism for shortening the duration of STAT3 activity, in turn shortening the duration of socs3 mRNA expression. Both STAT3WT and STAT3Ser727Asp (S727D) but not STAT3Ser727Ala (S727A) showed rapid dephosphorylation of pY705 after the inhibition of tyrosine kinases. We found that the nuclear TC45 phosphatase is most likely responsible for the phospho-S727-dependent pY705 dephosphorylation because TC45 knockdown caused prolonged pY705 with sustained socs3 mRNA expression in STAT3WT but not in STAT3S727A, and overexpressed TC45 caused rapid dephosphorylation of pY705 in STAT3WT but not in STAT3S727A. We further showed that phospho-S727 did not affect the interaction of TC45 with STAT3, and that a reported methylation at K140 of STAT3 occurring after phospho-S727 was not involved in the pY705 regulation. These findings indicate that phospho-Ser727 determines the duration of STAT3 activity largely through TC45.


Asunto(s)
Proteína Tirosina Fosfatasa no Receptora Tipo 2/metabolismo , Factor de Transcripción STAT3/metabolismo , ADN Polimerasa II/metabolismo , Regulación de la Expresión Génica , Células HEK293 , Células Hep G2 , Humanos , Mutación , Fosforilación , Regiones Promotoras Genéticas , Unión Proteica , ARN Mensajero/genética , Factor de Transcripción STAT3/genética , Serina/metabolismo , Proteína 3 Supresora de la Señalización de Citocinas , Proteínas Supresoras de la Señalización de Citocinas/genética
10.
Genes Cells ; 16(1): 34-45, 2011 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-21059157

RESUMEN

We previously reported that sirtuin 2 (SIRT2), a mammalian member of the NAD+-dependent protein deacetylases, participates in mitotic regulation, specifically, in efficient mitotic cell death caused by the spindle checkpoint. Here, we describe a novel function of SIRT2 that is different from mitotic regulation. SIRT2 down-regulation using siRNA caused apoptosis in cancer cell lines such as HeLa cells, but not in normal cells. The apoptosis was caused by p53 accumulation, which is mediated by p38 MAPK activation-dependent degradation of p300 and the subsequent MDM2 degradation. Sirtuin inhibitors are emerging as antitumor drugs, and this function has been ascribed to the inhibition of SIRT1, the most well-characterized sirtuin that deacetylases p53 to promote cell survival and also binds to other proteins in response to genotoxic stress. This study suggests that SIRT2 can be a novel molecular target for cancer therapy and provides a molecular basis for the efficacy of SIRT2 for future cancer therapy.


Asunto(s)
Apoptosis/genética , Regulación hacia Abajo , Sirtuina 2/metabolismo , Proteína p53 Supresora de Tumor/metabolismo , Proteínas Quinasas p38 Activadas por Mitógenos/metabolismo , Antineoplásicos/farmacología , Línea Celular , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/genética , Proteína p300 Asociada a E1A/metabolismo , Células HeLa , Humanos , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Sirtuinas/genética , Sirtuinas/metabolismo , Proteínas Quinasas p38 Activadas por Mitógenos/genética
11.
Mol Cell ; 24(1): 63-75, 2006 Oct 06.
Artículo en Inglés | MEDLINE | ID: mdl-17018293

RESUMEN

c-Fos is regulated by phosphorylation and multiple turnover mechanisms. We found that c-Fos was ubiquitylated in the cytoplasm during IL-6/gp130 stimulation under MEK inhibition and sought the mechanisms involved in the regulation. We show that sustained ERK5 activity and the E3 ligase UBR1 regulate the stability and subcellular localization of c-Fos. UBR1, rapidly induced by STAT3, interacts with and ubiquitylates c-Fos in the cytoplasm for its accelerated degradation. ERK5 inhibits the nuclear export of c-Fos by phosphorylating Thr232 in the c-Fos NES(221-233) and disrupts the interaction of c-Fos with UBR1 by phosphorylating Ser32. Moreover, UBR1 depletion in HeLa cells, which constitutively express UBR1 at a high level, enhances both c-Fos expression and cell growth, whereas ERK5 depletion reduces both of them. Interestingly, an NES mutant of c-Fos, but not wild-type, substitutes ERK5 activity for HeLa cell proliferation. Thus, this spatiotemporal regulation of c-Fos by ERK5 and UBR1 is critical for the regulation of c-Fos/AP-1.


Asunto(s)
Regulación de la Expresión Génica , Proteína Quinasa 7 Activada por Mitógenos/fisiología , Proteínas Proto-Oncogénicas c-fos/metabolismo , Ubiquitina-Proteína Ligasas/fisiología , Línea Celular , Proliferación Celular , Receptor gp130 de Citocinas/metabolismo , Flavonoides/farmacología , Células HeLa , Humanos , Interleucina-6/metabolismo , Quinasas de Proteína Quinasa Activadas por Mitógenos/antagonistas & inhibidores , Fosforilación , Mapeo de Interacción de Proteínas , Proteínas Proto-Oncogénicas c-fos/genética , Proteínas Proto-Oncogénicas c-fos/fisiología , Factor de Transcripción STAT3/metabolismo , Factor de Transcripción AP-1/metabolismo , Ubiquitina/metabolismo
12.
Proc Natl Acad Sci U S A ; 102(12): 4524-9, 2005 Mar 22.
Artículo en Inglés | MEDLINE | ID: mdl-15764709

RESUMEN

Signal transducer and activator of transcription 3 (STAT3) is activated by the IL-6 family of cytokines and growth factors. STAT3 requires phosphorylation on Ser-727, in addition to tyrosine phosphorylation on Tyr-705, to be transcriptionally active. In IL-6 signaling, the two major pathways that derive from the YXXQ and the YSTV motifs of gp130 cause Ser-727 phosphorylation. Here, we show that TGF-beta-activated kinase 1 (TAK1) interacts with STAT3, that the TAK1-Nemo-like kinase (NLK) pathway is efficiently activated by IL-6 through the YXXQ motif, and that this is the YXXQ-mediated H7-sensitive pathway that leads to STAT3 Ser-727 phosphorylation. Because NLK was recently shown to interact with STAT3, we explored the role of STAT3 in activating this pathway. Depletion of STAT3 diminished the IL-6-induced NLK activation by >80% without inhibiting IL-6-induced TAK1 activation or its nuclear entry. We found that STAT3 functioned as a scaffold for TAK1 and NLK in vivo through a region in its carboxyl terminus. Furthermore, the expression of the STAT3(534-770) region in the nuclei of STAT3-knockdown cells enhanced the IL-6-induced NLK activation in a dose-dependent manner but not the TGFbeta-induced NLK activation. TGFbeta did not cause STAT3 Ser-727 phosphorylation, even when the carboxyl region of STAT3 was expressed in the nuclei. Together, these results indicate that STAT3 enhances the efficiency of its own Ser-727 phosphorylation by acting as a scaffold for the TAK1-NLK kinases, specifically in the YXXQ motif-derived pathway.


Asunto(s)
Proteínas Portadoras/metabolismo , Proteínas de Unión al ADN/metabolismo , Quinasas Quinasa Quinasa PAM/metabolismo , Transactivadores/metabolismo , Secuencias de Aminoácidos , Secuencia de Aminoácidos , Secuencia de Bases , Sitios de Unión/genética , Proteínas Portadoras/química , Proteínas Portadoras/genética , Línea Celular , ADN/genética , Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/genética , Activación Enzimática/efectos de los fármacos , Humanos , Quinasa I-kappa B , Interleucina-6/farmacología , Quinasas Quinasa Quinasa PAM/química , Quinasas Quinasa Quinasa PAM/genética , Complejos Multiproteicos , Fosforilación , Interferencia de ARN , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Proteínas Recombinantes/farmacología , Factor de Transcripción STAT3 , Serina/química , Transducción de Señal/efectos de los fármacos , Transactivadores/química , Transactivadores/genética
13.
Biochem Biophys Res Commun ; 325(2): 541-8, 2004 Dec 10.
Artículo en Inglés | MEDLINE | ID: mdl-15530426

RESUMEN

STAT3 regulates many target genes in response to cytokines and growth factors. To study the mechanisms of STAT3-dependent transcription, we established several cell lines in which HepG2-STAT3-knockdown cells were reconstituted with a variety of STAT3 mutants. Using these cell lines, we found that truncated STAT3(1-750), but not STAT3(1-761), could not recruit SRC-1/NcoA-1 and was not phosphorylated on Ser727. Furthermore, mutation of STAT3 L755 and F757 to alanines caused the loss of STAT3-dependent SRC-1 recruitment, leaving Ser727 phosphorylation intact. Consistent with this, the STAT3-L755A/F757A mutant showed no increase in acetylated histone H3 at Lys14 and a decreased level of RNA polymerase II recruited to the target gene promoter, although p300 recruitment and histone H4 acetylation were intact. This mutant also lost responsiveness to co-expressed SRC-1. Thus, the conserved STAT3 region from 752 to 761, called STAT3 CR2, plays critical roles in STAT3-dependent transcription by recruiting SRC-1 and allowing Ser727 phosphorylation.


Asunto(s)
Proteínas de Unión al ADN/química , Proteínas de Unión al ADN/fisiología , Serina/metabolismo , Transactivadores/química , Transactivadores/fisiología , Factores de Transcripción/metabolismo , Secuencia de Aminoácidos , Animales , Línea Celular Tumoral , Secuencia Conservada , Proteínas de Unión al ADN/genética , Proteína p300 Asociada a E1A , Expresión Génica/fisiología , Histona Acetiltransferasas , Humanos , Interleucina-6/metabolismo , Leucina/genética , Leucina/metabolismo , Neoplasias Hepáticas/metabolismo , Ratones , Proteínas Nucleares/metabolismo , Coactivador 1 de Receptor Nuclear , Fenilalanina/genética , Fenilalanina/metabolismo , Fosforilación , Regiones Promotoras Genéticas/fisiología , Estructura Terciaria de Proteína , Proteínas Proto-Oncogénicas c-jun/genética , Proteínas Proto-Oncogénicas c-jun/metabolismo , Proteínas Recombinantes de Fusión/química , Proteínas Recombinantes de Fusión/genética , Proteínas Recombinantes de Fusión/metabolismo , Factor de Transcripción STAT3 , Transactivadores/genética , Transactivadores/metabolismo , Factores de Transcripción/genética , Transcripción Genética/fisiología
14.
Genes Cells ; 9(3): 233-42, 2004 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-15005710

RESUMEN

A STAT3 (signal transducer and activator of transcription 3)- and a MEK/Erk-mediated signal can be activated by cytokines, including IL-6 (interleukin-6), PDGF, and EGF. Recently, STAT3 and an ERK-signal were shown to co-operatively activate the c-fos gene. Activation of a truncated form of the IL-6 receptor subunit, gp130, that had only one YXXQ motif, induced both c-Fos and JunB in NIH3T3 cells through STAT3 without an apparent increase in the AP-1 (activator protein-1) activity. In contrast, concomitant stimulation of the STAT3 signal and a MEK/Erk-signal markedly increased AP-1 activity with enhanced c-Fos expression. Surprisingly, the c-Fos induced by the YXXQ-signal alone was localized to the cytoplasm, from which it translocated into the nucleus following TPA (12-O-tetradecanoyl-phorbol 13-acetate) treatment in a MEK/Erk-dependent manner. c-Fos that was expressed from a constitutive promoter localized to the nucleus and did not move into the cytoplasm in response to the YXXQ-signal. Rather, the YXXQ-signal was required during c-Fos production for it to be retained in the cytoplasm. Thus, the YXXQ-signal induces c-Fos expression through STAT3 and anchors the new c-Fos in the cytoplasm. In addition, the YXXQ-signal and an Erk signal co-operatively cause c-Fos activation in the nucleus.


Asunto(s)
Antígenos CD/química , Núcleo Celular/metabolismo , Proteínas de Unión al ADN/metabolismo , Glicoproteínas de Membrana/química , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Proteínas Quinasas Activadas por Mitógenos/metabolismo , Proteínas Proto-Oncogénicas c-fos/metabolismo , Transactivadores/metabolismo , Transporte Activo de Núcleo Celular , Secuencias de Aminoácidos , Animales , Antígenos CD/metabolismo , Línea Celular , Receptor gp130 de Citocinas , Citoplasma/metabolismo , Proteínas de Unión al ADN/genética , Ensayo de Cambio de Movilidad Electroforética , Regulación de la Expresión Génica , Factor Estimulante de Colonias de Granulocitos/metabolismo , Sistema de Señalización de MAP Quinasas , Glicoproteínas de Membrana/metabolismo , Ratones , Quinasas de Proteína Quinasa Activadas por Mitógenos/genética , Proteínas Quinasas Activadas por Mitógenos/genética , Transporte de Proteínas , Proteínas Proto-Oncogénicas c-fos/biosíntesis , Proteínas Proto-Oncogénicas c-fos/genética , Proteínas Proto-Oncogénicas c-jun/genética , Proteínas Proto-Oncogénicas c-jun/metabolismo , Factor de Transcripción STAT3 , Transducción de Señal , Antígeno Polipéptido de Tejido/metabolismo , Transactivadores/genética , Factor de Transcripción AP-1/genética , Factor de Transcripción AP-1/metabolismo
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