RESUMEN
The inhibitor of apoptosis proteins (IAPs) have been shown to interact with a growing number of intracellular proteins and pathways to fulfil their anti-apoptotic role. In the search for novel IAP-interacting proteins we identified the neurotrophin receptor-interacting MAGE homologue (NRAGE) as being able to bind to the avian IAP homologue ITA. This interaction requires the RING domain of ITA. NRAGE additionally coimmunoprecipitates with XIAP. When overexpressed in 32D cells NRAGE augments interleukin-3 withdrawal induced apoptosis, possibly through binding endogenous XIAP. Moreover, NRAGE is able to overcome the anti-apoptotic effect of Bcl-2.
Asunto(s)
Apoptosis/fisiología , Proteínas de Unión al ADN/metabolismo , Proteínas de Neoplasias , Proteínas/metabolismo , Animales , Sitios de Unión , Aves , Dimerización , Regulación de la Expresión Génica , Proteínas Inhibidoras de la Apoptosis , Proteínas de Insectos , Interleucina-3/deficiencia , Ratones , Unión Proteica , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , Células Tumorales Cultivadas , Proteína Inhibidora de la Apoptosis Ligada a XRESUMEN
Extracellular signal regulated kinase 5 (ERK5) is a novel member of the mitogen-activated protein kinase (MAPK) family with a poorly defined physiological function. Since ERK5 and its upstream activator MEK5 are abundant in skeletal muscle we examined a function of the cascade during muscle differentiation. We show that ERK5 is activated upon induction of differentiation in mouse myoblasts and that selective activation of the pathway results in promoter activation of differentiation-specific genes. Moreover, myogenic differentiation is completely blocked when ERK5 expression is inhibited by antisense RNA. Thus, we conclude that the MEK5/ERK5 MAP kinase cascade is critical for early steps of muscle cell differentiation.
Asunto(s)
Proteínas Quinasas Activadas por Mitógenos/metabolismo , Músculos/citología , Animales , Western Blotting , Diferenciación Celular , Línea Celular , Activación Enzimática , Genes Dominantes , Genes Reporteros , Humanos , MAP Quinasa Quinasa 5 , Sistema de Señalización de MAP Quinasas , Ratones , Proteína Quinasa 7 Activada por Mitógenos , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Músculo Esquelético/citología , Oligonucleótidos Antisentido/metabolismo , Regiones Promotoras Genéticas , ARN Mensajero/metabolismo , Transducción de Señal , Factores de Tiempo , Transducción Genética , TransfecciónRESUMEN
In the search for physiological substrates of MAPK-activated protein (MAPKAP) kinases, we identified the basic helix-loop-helix (bHLH) transcription factor E47 as an interaction partner of chromosome 3p kinase (3pK) and MAPKAP-K2 (MK2). The E2A protein E47 is known to be involved in the regulation of tissue-specific gene expression and cell differentiation. E47 is a phosphoprotein, and we identified 3pK and MK2 as E47 kinases in vitro. Furthermore, the expression of either kinase results in a repression of the transcriptional activity of E47 on an E-box containing promoter. In summary, the MAPK-activated protein kinases 3pK and MK2 were identified to form an assembly with the bHLH protein E47 suggesting that these kinases are regulators of E47 activity and E47-dependent gene expression.
Asunto(s)
Proteínas de Unión al ADN/metabolismo , Quinasas de Proteína Quinasa Activadas por Mitógenos/metabolismo , Proteínas Serina-Treonina Quinasas/metabolismo , Proteínas Tirosina Quinasas/metabolismo , Proteínas Represoras/metabolismo , Factores de Transcripción , Animales , Secuencia de Bases , Línea Celular , Proteínas de Unión al ADN/genética , Regulación de la Expresión Génica , Genes Reporteros , Humanos , Péptidos y Proteínas de Señalización Intracelular , MAP Quinasa Quinasa 2 , Datos de Secuencia Molecular , Fosforilación , Pruebas de Precipitina , Regiones Promotoras Genéticas , Unión Proteica , Proteínas Serina-Treonina Quinasas/genética , Proteínas Recombinantes , Factores de Transcripción TCF , Proteína 1 Similar al Factor de Transcripción 7 , Activación Transcripcional/genética , Transfección , LevadurasRESUMEN
To study the role of MAPK cascades in the regulation of naturally occurring human immunodeficiency virus type 1 long terminal repeats (HIV-1 LTRs), we analyzed several HIV-1 LTRs from patients at different stages of disease progression. One of these naturally occurring HIV-1 LTRs contains an insertion termed the most frequent naturally occurring length polymorphism (MFNLP) and exhibited high inducibility upon T cell activation. We found that the protein kinase mixed lineage kinase 3/src-homology 3 domain-containing proline-rich kinase, a specific activator of the stress-activated protein kinase (SAPK)/JNK signaling pathway in T lymphocytes, induces high transcriptional activation of this promoter. Promoter inducibility is inhibited by the SAPK/JNK inhibitor, the JNK binding domain of the JNK interacting protein 1, and Tam-67 (N-terminal deletion mutant of c-Jun). In electrophoretic mobility shift assay, several protein complexes were found to bind to the MFNLP sequence in T cells. We identified AP-1 factors c-Fos and JunB as MFNLP-binding proteins, whose binding is abolished by introducing point mutations in the 3'-half of the MFNLP sequence. Introduction of these point mutations into the MFNLP containing HIV-1 LTR reduced src-homology 3 domain-containing proline-rich kinase -mediated transactivation. These data indicate that the AP-1-like binding site in the MFNLP sequence gives rise to a higher inducibility of natural HIV-LTRs by the SAPK/JNK signaling pathway.