RESUMO
The Hippo pathway is an important regulator of organ growth and cell fate. The major mechanism by which Hippo is known to control transcription is by dictating the nucleo-cytoplasmic shuttling rate of Yorkie, a transcription co-activator, which promotes transcription with the DNA binding protein Scalloped. The nuclear biophysical behavior of Yorkie and Scalloped, and whether this is regulated by the Hippo pathway, remains unexplored. Using multiple live-imaging modalities on Drosophila tissues, we found that Scalloped interacts with DNA on a broad range of timescales, and enrichment of Scalloped at sites of active transcription is mediated by longer DNA dwell times. Further, Yorkie increased Scalloped's DNA dwell time, whereas the repressors Nervous fingers 1 (Nerfin-1) and Tondu-domain-containing growth inhibitor (Tgi) decreased it. Therefore, the Hippo pathway influences transcription not only by controlling nuclear abundance of Yorkie but also by modifying the DNA binding kinetics of the transcription factor Scalloped.
Assuntos
Cromatina , Proteínas de Drosophila , Drosophila melanogaster , Proteínas Serina-Treonina Quinases , Transdução de Sinais , Transativadores , Transcrição Gênica , Proteínas de Sinalização YAP , Animais , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Cromatina/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Serina-Treonina Quinases/genética , Drosophila melanogaster/metabolismo , Drosophila melanogaster/genética , Proteínas de Sinalização YAP/metabolismo , Transativadores/metabolismo , Transativadores/genética , Fatores de Transcrição/metabolismo , Fatores de Transcrição/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , Proteínas Nucleares/metabolismo , Proteínas Nucleares/genética , Ligação Proteica , Núcleo Celular/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , DNA/metabolismo , DNA/genéticaRESUMO
Organ size is controlled by numerous factors including mechanical forces, which are mediated in part by the Hippo pathway. In growing Drosophila epithelial tissues, cytoskeletal tension influences Hippo signaling by modulating the localization of key pathway proteins to different apical domains. Here, we discovered a Hippo signaling hub at basal spot junctions, which form at the basal-most point of the lateral membranes and resemble adherens junctions in protein composition. Basal spot junctions recruit the central kinase Warts via Ajuba and E-cadherin, which prevent Warts activation by segregating it from upstream Hippo pathway proteins. Basal spot junctions are prominent when tissues undergo morphogenesis and are highly sensitive to fluctuations in cytoskeletal tension. They are distinct from focal adhesions, but the latter profoundly influences basal spot junction abundance by modulating the basal-medial actomyosin network and tension experienced by spot junctions. Thus, basal spot junctions couple morphogenetic forces to Hippo pathway activity and organ growth.