RESUMO
Oncogenic transcription factor FOXQ1 has been implicated in promotion of multiple transformed phenotypes in carcinoma cells. Recently, we have characterized FOXQ1 as a melanoma tumor suppressor that acts via repression of N-cadherin gene, and invasion and metastasis. Here we report that FOXQ1 induces differentiation in normal and transformed melanocytic cells at least partially via direct transcriptional activation of MITF gene, melanocytic lineage-specific regulator of differentiation. Importantly, we demonstrate that pigmentation induced in cultured melanocytic cells and in mice by activation of cAMP/CREB1 pathway depends in large part on FOXQ1. Moreover, our data reveal that FOXQ1 acts as a critical mediator of BRAFV600E-dependent regulation of MITF levels, thus providing a novel link between two major signal transduction pathways controlling MITF and differentiation in melanocytic cells.
Assuntos
Fatores de Transcrição Forkhead/metabolismo , Melanócitos/metabolismo , Melanoma/metabolismo , Transdução de Sinais , Neoplasias Cutâneas/metabolismo , Animais , Linhagem Celular Tumoral , Fatores de Transcrição Forkhead/genética , Melanócitos/patologia , Melanoma/genética , Melanoma/patologia , Camundongos , Camundongos Knockout , Fator de Transcrição Associado à Microftalmia/genética , Fator de Transcrição Associado à Microftalmia/metabolismo , Proteínas Proto-Oncogênicas B-raf/genética , Proteínas Proto-Oncogênicas B-raf/metabolismo , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/patologiaRESUMO
GTP is a major regulator of multiple cellular processes, but tools for quantitative evaluation of GTP levels in live cells have not been available. We report the development and characterization of genetically encoded GTP sensors, which we constructed by inserting a circularly permuted yellow fluorescent protein (cpYFP) into a region of the bacterial G protein FeoB that undergoes a GTP-driven conformational change. GTP binding to these sensors results in a ratiometric change in their fluorescence, thereby providing an internally normalized response to changes in GTP levels while minimally perturbing those levels. Mutations introduced into FeoB to alter its affinity for GTP created a series of sensors with a wide dynamic range. Critically, in mammalian cells the sensors showed consistent changes in ratiometric signal upon depletion or restoration of GTP pools. We show that these GTP evaluators (GEVALs) are suitable for detection of spatiotemporal changes in GTP levels in living cells and for high-throughput screening of molecules that modulate GTP levels.