RESUMEN
Hox genes encode transcription factors widely used for diversifying animal body plans in development and evolution. To achieve functional specificity, Hox proteins associate with PBC class proteins, Pre-B cell leukemia homeobox (Pbx) in vertebrates, and Extradenticle (Exd) in Drosophila, and were thought to use a unique hexapeptide-dependent generic mode of interaction. Recent findings, however, revealed the existence of an alternative, UbdA-dependent paralog-specific interaction mode providing diversity in Hox-PBC interactions. In this study, we investigated the basis for the selection of one of these two Hox-PBC interaction modes. Using naturally occurring variations and mutations in the Drosophila Ultrabithorax protein, we found that the linker region, a short domain separating the hexapeptide from the homeodomain, promotes an interaction mediated by the UbdA domain in a context-dependent manner. While using a UbdA-dependent interaction for the repression of the limb-promoting gene Distalless, interaction with Exd during segment-identity specification still relies on the hexapeptide motif. We further show that distinctly assembled Hox-PBC complexes display subtle but distinct repressive activities. These findings identify Hox-PBC interaction as a template for subtle regulation of Hox protein activity that may have played a major role in the diversification of Hox protein function in development and evolution.
Asunto(s)
Proteínas de Drosophila/metabolismo , Evolución Molecular , Proteínas de Homeodominio/metabolismo , Factores de Transcripción/metabolismo , Secuencias de Aminoácidos , Animales , Proteínas de Drosophila/genética , Drosophila melanogaster , Proteínas de Homeodominio/genética , Estructura Terciaria de Proteína , Factores de Transcripción/genéticaRESUMEN
Protein function is encoded within protein sequence and protein domains. However, how protein domains cooperate within a protein to modulate overall activity and how this impacts functional diversification at the molecular and organism levels remains largely unaddressed. Focusing on three domains of the central class Drosophila Hox transcription factor AbdominalA (AbdA), we used combinatorial domain mutations and most known AbdA developmental functions as biological readouts to investigate how protein domains collectively shape protein activity. The results uncover redundancy, interactivity, and multifunctionality of protein domains as salient features underlying overall AbdA protein activity, providing means to apprehend functional diversity and accounting for the robustness of Hox-controlled developmental programs. Importantly, the results highlight context-dependency in protein domain usage and interaction, allowing major modifications in domains to be tolerated without general functional loss. The non-pleoitropic effect of domain mutation suggests that protein modification may contribute more broadly to molecular changes underlying morphological diversification during evolution, so far thought to rely largely on modification in gene cis-regulatory sequences.
Asunto(s)
Tipificación del Cuerpo/genética , Sistema Nervioso Central/embriología , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/genética , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Animales , Linaje de la Célula/genética , Sistema Nervioso Central/crecimiento & desarrollo , Proteínas de Unión al ADN/genética , Proteínas de Drosophila/química , Drosophila melanogaster/embriología , Drosophila melanogaster/crecimiento & desarrollo , Regulación del Desarrollo de la Expresión Génica , Estudios de Asociación Genética , Mutación , Proteínas Nucleares/química , Estructura Terciaria de Proteína/genética , Factores de Transcripción/química , Proteína Wnt1/genética , Proteína Wnt1/metabolismoRESUMEN
The Ikaros transcription factor is a tumor suppressor that is also important for lymphocyte development. How post-translational modifications influence Ikaros function remains partially understood. We show that Ikaros undergoes sumoylation in developing T cells that correspond to mono-, bi- or poly-sumoylation by SUMO1 and/or SUMO2/3 on three lysine residues (K58, K240 and K425). Sumoylation occurs in the nucleus and requires DNA binding by Ikaros. Sumoylated Ikaros is less effective than unsumoylated forms at inhibiting the expansion of murine leukemic cells, and Ikaros sumoylation is abundant in human B-cell acute lymphoblastic leukemic cells, but not in healthy peripheral blood leukocytes. Our results suggest that sumoylation may be important in modulating the tumor suppressor function of Ikaros.
Asunto(s)
Proteínas de Unión al ADN/genética , Factor de Transcripción Ikaros/genética , Leucemia-Linfoma Linfoblástico de Células Precursoras/genética , Transcripción Genética , Animales , Linfocitos B/patología , Línea Celular Tumoral , Proteínas de Unión al ADN/biosíntesis , Regulación Neoplásica de la Expresión Génica , Humanos , Factor de Transcripción Ikaros/biosíntesis , Linfocitos/patología , Ratones , Leucemia-Linfoma Linfoblástico de Células Precursoras/patología , Procesamiento Proteico-Postraduccional/genética , Proteína SUMO-1/genética , Sumoilación/genética , Proteínas Supresoras de TumorRESUMEN
Hox proteins have well-established functions in development and evolution, controlling the final morphology of bilaterian animals. The common phylogenetic origin of Hox proteins and the associated evolutionary diversification of protein sequences provide a unique framework to explore the relationship between changes in protein sequence and function. In this study, we aimed at questioning how sequence variation within arthropod Hox proteins influences function. This was achieved by exploring the functional impact of sequence conservation/divergence of the Hox genes, labial, Sex comb reduced, Deformed, Ultrabithorax and abdominalA from two distant arthropods, the sea spider and the well-studied Drosophila. Results highlight a correlation between sequence conservation within the homeodomain and the degree of functional conservation, and identify a novel functional domain in the Labial protein.