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General Comment |
Mask proteins are cofactors of Yorkie/YAP in the Hippo pathway. Sidor CM et al. The Hippo signaling pathway acts via the Yorkie (Yki)/Yes-associated protein (YAP) transcriptional coactivator family to control tissue growth in both Drosophila and mammals 1-3]. Yki/YAP drives tissue growth by activating target gene transcription, but how it does so remains unclear. Here we identify Mask as a novel cofactor for Yki/YAP. We show that Drosophila Mask forms a complex with Yki and its binding partner, Scalloped (Sd), on target-gene promoters and is essential for Yki to drive transcription of target genes and tissue growth. Furthermore, the stability and subcellular localization of both Mask and Yki is coregulated in response to various stimuli. Finally, Mask proteins are functionally conserved between Drosophila and humans and are coexpressed with YAP in a wide variety of human stem/progenitor cells and tumors.
Mask is required for the activity of the Hippo pathway effector Yki/YAP. [Sansores-Garcia L 2013 et al.
The Drosophila Yorkie (Yki) protein and its mammalian homolog Yes-associated protein (YAP) are potent growth promoters, and YAP overexpression is associated with multiple types of cancer. Yki and YAP are transcriptional coactivators and function as downstream effectors of the Hippo tumor suppressor pathway. The regulation of Yki and YAP by the Hippo signaling pathway has been extensively investigated; however, how they regulate gene expression is poorly understood. To identify additional regulators of Yki activity, we performed a genome-wide RNAi screen in Drosophila S2 cells. In this screen, we identified the conserved protein Mask (Multiple ankyrin repeats single KH domain) as a novel promoter of Yki activity in vitro and validated this function in vivo in Drosophila. We found that Mask is required downstream of the Hippo pathway for Yki to induce target-gene expression and that Mask forms complexes with Yki. The human Mask homolog MASK1 complexes with YAP and is required for the full activity of YAP. Additionally, elevated MASK1 expression is associated with worsened outcomes for breast cancer patients. We conclude that Mask is a novel cofactor for Yki/YAP required for optimal Yki/YAP activity during development and oncogenesis.
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NCBI Summary:
This gene encodes a protein with multiple ankyrin repeat domains and a single KH-domain. The protein is thought to function as a scaffolding protein, and it may be involved in the regulation of caspases and thereby play an antiapoptotic role in cell survival. Alternative splicing results in multiple transcript variants, one of which generates a fusion transcript (MASK-BP3) with the downstream eIF4E-binding protein 3 (EIF4EBP3) gene, resulting in a protein comprised of the ANKHD1 sequence for the majority of the protein and a different C-terminus due to an alternate reading frame for the EIF4EBP3 segments. [provided by RefSeq, Sep 2010]
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