RESUMEN
While studies have highlighted the role of HOXA9-13 and PBX1 homeobox genes during the development of the female genital tract, the molecular mechanisms triggered by these genes are incompletely elucidated. In several developmental pathways, PBX1 binds to MEINOX family members in the cytoplasm to be imported into the nucleus where they associate with HOX proteins to form a higher complex that modulates gene expression. This concept has been challenged by a recent report showing that in some cell cultures, PBX1 nuclear localization might be regulated independently of MEINOX proteins (Kilstrup-Nielsen et al., 2003). Our work gives the first illustration of this alternative mechanism in an organogenesis process. Indeed, we show that PBX1 is mostly cytoplasmic in epithelial endometrial cells of the developing female genital tract despite the nuclear localization of MEIS1. We thus provide evidence for a control of PBX1 intracellular distribution which is independent of MEINOX proteins, but is cell cycle correlated.
Asunto(s)
Células Epiteliales/metabolismo , Genitales Femeninos/embriología , Genitales Femeninos/metabolismo , Proteínas de Homeodominio/metabolismo , Proteínas de Neoplasias/metabolismo , Factores de Transcripción/metabolismo , Animales , Ciclo Celular , Línea Celular , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Células Epiteliales/citología , Femenino , Regulación de la Expresión Génica , Regulación del Desarrollo de la Expresión Génica , Genitales Femeninos/citología , Proteínas de Homeodominio/genética , Humanos , Ratones , Proteína 1 del Sitio de Integración Viral Ecotrópica Mieloide , Proteínas de Neoplasias/genética , Factor de Transcripción 1 de la Leucemia de Células Pre-B , Transporte de Proteínas , Factores de Transcripción/genéticaRESUMEN
Various Hox genes are known to produce alternative transcripts encoding different isoforms whose physiological relevance during development is not yet understood. In this work, we analysed two different Hoxa9 mRNAs encoding a full-length protein (Hoxa9) or a protein lacking the homeodomain (Hoxa9T). First, we demonstrated that these transcripts are conserved from birds to mammals. We then showed that both transcripts are present throughout embryogenesis and that Hoxa9T transcript is particularly abundant in embryonic genital tract, kidney, forelimb and tail. We further found that both isoforms are able to interact with CBP, suggesting a competition between Hoxa9 and Hoxa9T with this protein.
Asunto(s)
Proteínas de Homeodominio/metabolismo , Isoformas de Proteínas/metabolismo , Animales , Secuencia de Bases , Embrión de Pollo , Genes Reporteros , Proteínas de Homeodominio/genética , Humanos , Proteínas de la Membrana/metabolismo , Ratones , Datos de Secuencia Molecular , Fosfoproteínas/metabolismo , Isoformas de Proteínas/genética , ARN Mensajero/genética , Alineación de Secuencia , Análisis de Secuencia de ARNRESUMEN
The chromatin high mobility group protein 1 (HMGB1) is a very abundant and conserved protein that is structured into two HMG box domains plus a highly acidic C-terminal domain. From the ability to bind DNA nonspecifically and to interact with various proteins, several functions in DNA-related processes have been assigned to HMGB1. Nevertheless, its functional role remains the subject of controversy. Using a phage display approach we have shown that HMGB1 can recognize several peptide motifs. A computer search of the protein data bases found peptide homologies with proteins already known to interact with HMGB1, like p53, and have allowed us to identify new potential candidates. Among them, transcriptional activators like the heterogeneous nuclear ribonucleoprotein K (hnRNP K), repressors like methyl-CpG binding protein 2 (MeCP2), and co-repressors like the retinoblastoma susceptibility protein (pRb) and Groucho-related gene proteins 1 (Grg1) and 5 (Grg5) can be found. A detailed analysis of the interaction of Grg1 with HMGB1 confirmed that the binding region contained the sequence homologous to one of the peptides identified. Our results have led us to propose that HMGB1 may play a central role in the stabilization and/or assembly of several multifunctional complexes through protein-protein interactions.