Novel Antennapedia and Ultrabithorax trimeric complexes with TBP and Exd regulate transcription.

BACKGROUND: Hox proteins interact with DNA and many other proteins, co-factors, transcriptional factors, chromatin remodeling components, non-coding RNAs and even the extracellular matrix that assembles the Hox complexes. The number of interacting partners continues to grow with diverse components and more transcriptional factors than initially thought. Hox complexes present many activities, but their molecular mechanisms to modulate their target genes remain unsolved. RESULTS: In this paper we showed the protein-protein interaction of Antp with Ubx through the homeodomain using BiFC in Drosophila. Analysis of Antp-deletional mutants showed that AntpHD helixes 1 and 2 are required for the interaction with Ubx. Also, we found a novel interaction of Ubx with TBP, in which the PolyQ domain of TBP is required for the interaction. Moreover, we also detected the formation of two new trimeric complexes of Antp with Ubx, TBP and Exd using BiFC-FRET; these proteins, however, do not form a trimeric interaction with BIP2 or TFIIEß. The novel trimeric complexes reduced Antp transcriptional activity, indicating that they could confer specificity for repression. CONCLUSIONS: Our results increase the number of transcriptional factors in the Antp and Ubx interactomes that form two novel trimeric complexes with TBP and Exd. We also report a new Ubx interaction with TBP. These novel interactions provide important clues of the dynamics of Hox-interacting complexes involved in transcriptional regulation, contributing to better understand Hox function.

Drosophila in the study of hTBP protein interactions in the development and modeling of SCA17.

BACKGROUND: Protein interactions participate in many molecular mechanisms involved in cellular processes. The human TATA box binding protein (hTBP) interacts with Antennapedia (Antp) through its N-terminal region, specifically via its glutamine homopeptides. This PolyQ region acts as a binding site for other transcription factors under normal conditions, but when it expands, it generates spinocerebellar ataxia 17 (SCA17), whose protein aggregates in the brain prevent its correct functioning. OBJECTIVE: To determine whether the hTBP glutamine-rich region is involved in its interaction with homeoproteins and the role it plays in the formation of protein aggregates in SCA17. MATERIAL AND METHODS: We characterized hTBP interaction with other homeoproteins using BiFC, and modeled SCA17 in Drosophila melanogaster by targeting hTBPQ80 to the fly brain using UAS/GAL4. RESULTS: There was hTBP interaction with homeoproteins through its glutamine-rich region, and hTBP protein aggregates with expanded glutamines were found to affect the locomotor capacity of flies. CONCLUSIONS: The study of hTBP interactions opens the possibility for the search for new therapeutic strategies in neurodegenerative pathologies such as SCA17.

ANTECEDENTES: Las interacciones proteicas participan en una gran cantidad de mecanismos moleculares que rigen los procesos celulares. La proteína de unión a la caja TATA humana (hTBP) interacciona con Antennapedia (Antp) a través de su extremo N-terminal, específicamente a través de sus homopéptidos de glutaminas. Esta región PolyQ sirve como sitio de unión a factores de transcripción en condiciones normales, pero cuando se expande genera la ataxia espinal cerebelosa 17 (SCA17), cuyos agregados proteicos en el cerebro impiden su funcionamiento correcto. OBJETIVO: Determinar si la región rica en glutaminas de hTBP interviene en su interacción con homeoproteínas y el papel que tiene en la formación de agregados proteicos en SCA17. MATERIAL Y MÉTODOS: Se caracterizó la interacción de hTBP con otras homeoproteínas usando BiFC y se modeló SCA17 en Drosophila melanogaster dirigiendo hTBPQ80 al cerebro de las moscas usando UAS/GAL4. RESULTADOS: Existió interacción de hTBP con homeoproteínas a través de su región rica en glutaminas. Los agregados proteicos de hTBP con las glutaminas expandidas afectaron la capacidad locomotriz de las moscas. CONCLUSIONES: El estudio de las interacciones de hTBP abre la posibilidad para la búsqueda de nuevas estrategias terapéuticas en patologías neurodegenerativas como SCA17.

Trimeric complexes of Antp-TBP with TFIIEß or Exd modulate transcriptional activity.

BACKGROUND: Hox proteins finely coordinate antero-posterior axis during embryonic development and through their action specific target genes are expressed at the right time and space to determine the embryo body plan. As master transcriptional regulators, Hox proteins recognize DNA through the homeodomain (HD) and interact with a multitude of proteins, including general transcription factors and other cofactors. HD binding specificity increases by protein-protein interactions with a diversity of cofactors that outline the Hox interactome and determine the transcriptional landscape of the selected target genes. All these interactions clearly demonstrate Hox-driven transcriptional regulation, but its precise mechanism remains to be elucidated. RESULTS: Here we report Antennapedia (Antp) Hox protein-protein interaction with the TATA-binding protein (TBP) and the formation of novel trimeric complexes with TFIIEß and Extradenticle (Exd), as well as its participation in transcriptional regulation. Using Bimolecular Fluorescence Complementation (BiFC), we detected the interaction of Antp-TBP and, in combination with Förster Resonance Energy Transfer (BiFC-FRET), the formation of the trimeric complex with TFIIEß and Exd in living cells. Mutational analysis showed that Antp interacts with TBP through their N-terminal polyglutamine-stretches. The trimeric complexes of Antp-TBP with TFIIEß and Exd were validated using different Antp mutations to disrupt the trimeric complexes. Interestingly, the trimeric complex Antp-TBP-TFIIEß significantly increased the transcriptional activity of Antp, whereas Exd diminished its transactivation. CONCLUSIONS: Our findings provide important insights into the Antp interactome with the direct interaction of Antp with TBP and the two new trimeric complexes with TFIIEß and Exd. These novel interactions open the possibility to analyze promoter function and gene expression to measure transcription factor binding dynamics at target sites throughout the genome.

Drosophila en el estudio de las interacciones proteicas de hTBP en el desarrollo y modelaje de SCA17 / Drosophila in the study of hTBP protein interactions in the development and modeling of SCA17

Resumen Antecedentes: Las interacciones proteicas participan en una gran cantidad de mecanismos moleculares que rigen los procesos celulares. La proteína de unión a la caja TATA humana (hTBP) interacciona con Antennapedia (Antp) a través de su extremo N-terminal, específicamente a través de sus homopéptidos de glutaminas. Esta región PolyQ sirve como sitio de unión a factores de transcripción en condiciones normales, pero cuando se expande genera la ataxia espinal cerebelosa 17 (SCA17), cuyos agregados proteicos en el cerebro impiden su funcionamiento correcto. Objetivo: Determinar si la región rica en glutaminas de hTBP interviene en su interacción con homeoproteínas y el papel que tiene en la formación de agregados proteicos en SCA17. Material y métodos: Se caracterizó la interacción de hTBP con otras homeoproteínas usando BiFC y se modeló SCA17 en Drosophila melanogaster dirigiendo hTBPQ80 al cerebro de las moscas usando UAS/GAL4. Resultados: Existió interacción de hTBP con homeoproteínas a través de su región rica en glutaminas. Los agregados proteicos de hTBP con las glutaminas expandidas afectaron la capacidad locomotriz de las moscas. Conclusiones: El estudio de las interacciones de hTBP abre la posibilidad para la búsqueda de nuevas estrategias terapéuticas en patologías neurodegenerativas como SCA17.

Abstract Background: Protein interactions participate in many molecular mechanisms involved in cellular processes. The human TATA box binding protein (hTBP) interacts with Antennapedia (Antp) through its N-terminal region, specifically via its glutamine homopeptides. This PolyQ region acts as a binding site for other transcription factors under normal conditions, but when it expands, it generates spinocerebellar ataxia 17 (SCA17), whose protein aggregates in the brain prevent its correct functioning. Objective: To determine whether the hTBP glutamine-rich region is involved in its interaction with homeoproteins and the role it plays in the formation of protein aggregates in SCA17. Material and methods: We characterized hTBP interaction with other homeoproteins using BiFC, and modeled SCA17 in Drosophila melanogaster by targeting hTBPQ80 to the fly brain using UAS/GAL4. Results: There was hTBP interaction with homeoproteins through its glutamine-rich region, and hTBP protein aggregates with expanded glutamines were found to affect the locomotor capacity of flies. Conclusions: The study of hTBP interactions opens the possibility for the search for new therapeutic strategies in neurodegenerative pathologies such as SCA17.