The Hippo pathway has been implicated in suppressing tissue overgrowth and tumor formation by restricting the oncogenic activity of YAP. However, transcriptional regulators that inhibit YAP activity have not been well studied. Here, we uncover clinical importance for VGLL4 in gastric cancer suppression and find that VGLL4 directly competes with YAP for binding TEADs. Importantly, VGLL4's tandem Tondu domains are not only essential but also sufficient for its inhibitory activity toward YAP. A peptide mimicking this function of VGLL4 potently suppressed tumor growth in vitro and in vivo. These findings suggest that disruption of YAP-TEADs interaction by a VGLL4-mimicking peptide may be a promising therapeutic strategy against YAP-driven human cancers.

Hedgehog (HH) morphogen is essential for metazoan development. The seven-transmembrane protein smoothened (SMO) transduces the HH signal across the plasma membrane, but how SMO is activated remains poorly understood. In Drosophila melanogaster, HH induces phosphorylation at multiple Ser/Thr residues in the SMO carboxy-terminal cytoplasmic tail, leading to its cell surface accumulation and activation. Here we provide evidence that phosphorylation activates SMO by inducing a conformational switch. This occurs by antagonizing multiple Arg clusters in the SMO cytoplasmic tail. The Arg clusters inhibit SMO by blocking its cell surface expression and keeping it in an inactive conformation that is maintained by intramolecular electrostatic interactions. HH-induced phosphorylation disrupts the interaction, and induces a conformational switch and dimerization of SMO cytoplasmic tails, which is essential for pathway activation. Increasing the number of mutations in the Arg clusters progressively activates SMO. Hence, by employing multiple Arg clusters as inhibitory elements counteracted by differential phosphorylation, SMO acts as a rheostat to translate graded HH signals into distinct responses.The HH morphogen controls many key development processes, with different thresholds specifying distinct outcomes [1][2][3][4] . In Drosophila wing discs, HH proteins secreted by posterior (P) compartment cells move into the anterior (A) compartment to form a local concentration gradient 5,6 . Low levels of HH suffice to induce the expression of decapentaplegic (dpp), whereas high levels are required to induce patched (ptc) and engrailed (en) ( Supplementary Fig. 1) [7][8][9] .The reception system for HH consists of a twelve-transmembrane protein, PTC, as the HH receptor and a seven-transmembrane protein smoothened (SMO) as the signal transducer 10-13 . In Drosophila, HH binding to PTC abrogates its inhibition on SMO and induces extensive phosphorylation of the SMO cytoplasmic tail by protein kinase A (PKA) and casein kinase I (CKI), leading to SMO cell surface accumulation and activation [14][15][16][17] . How phosphorylation promotes SMO cell surface accumulation is not understood. In addition, phosphorylation may regulate SMO activity through mechanism(s) other than controlling its cell surface abundance. Regulation of SMO by multiple Arg clustersOur previous study indicates that phosphorylation may regulate SMO cell surface abundance by either preventing its endocytosis and/or promoting its recycling 15 . To investigate further how SMO cell surface expression is regulated, we generated a set of C-terminally truncated SMO variants and examined their subcellular localization using a cell-based assay (Fig. 1). Deletion up to amino acid 818 did not significantly change SMO subcellular distribution; however, further deletions resulted in progressively increased cell surface expression (Fig. 1a, c), implying that multiple negative regulatory elements exist between amino acids 661-818.SMODC710 exhibits consistently higher cell surface...

A variety of organisms have evolved mechanisms to detect and respond to light, in which the response is mediated by protein structural changes following photon absorption. The initial step is often the photo-isomerization of a conjugated chromophore. Isomerization occurs on ultrafast timescales, and is substantially influenced by the chromophore environment. Here we identify structural changes associated with the earliest steps in the trans to cis isomerization of the chromophore in photoactive yellow protein. Femtosecond, hard X-ray pulses emitted by the Linac Coherent Light Source were used to conduct time-resolved serial femtosecond crystallography on PYP microcrystals over the time range from 100 femtoseconds to 3 picoseconds to determine the structural dynamics of the photoisomerization reaction.