The Drosophila TEAD ortholog Scalloped is required for Yki-mediated overgrowth but is largely dispensable for normal tissue growth, suggesting that its mammalian counterpart may be exploited for selective inhibition of oncogenic growth driven by YAP hyperactivation. Here we test this hypothesis genetically and pharmacologically. We show that a dominant-negative TEAD molecule does not perturb normal liver growth but potently suppresses hepatomegaly/tumorigenesis resulting from YAP overexpression or Neurofibromin 2 (NF2)/Merlin inactivation. We further identify verteporfin as a small molecule that inhibits TEAD-YAP association and YAPinduced liver overgrowth. These findings provide proof of principle that inhibiting TEAD-YAP interactions is a pharmacologically viable strategy against the YAP oncoprotein.

The Hippo (Hpo) kinase cascade restricts tissue growth by inactivating the transcriptional coactivator Yorkie (Yki), which regulates the expression of target genes such as the cell death inhibitor diap1 by unknown mechanisms. Here we identify the TEAD/TEF family protein Scalloped (Sd) as a DNA-binding transcription factor that partners with Yki to mediate the transcriptional output of the Hpo growth-regulatory pathway. The diap1 (th) locus harbors a minimal Sd-binding Hpo Responsive Element (HRE) that mediates transcriptional regulation by the Hpo pathway. Sd binds directly to Yki, and a Yki missense mutation that abrogates Sd-Yki binding also inactivates Yki function in vivo. We further demonstrate that sd is required for yki-induced tissue overgrowth and target gene expression, and that sd activity is conserved in its mammalian homolog. Our results uncover a heretofore missing link in the Hpo signaling pathway and provide a glimpse of the molecular events on a Hpo-responsive enhancer element.

Antiretroviral therapy can reduce human immunodeficiency virus type 1 (HIV-1) viremia to below the detection limit of ultrasensitive clinical assays (50 copies of HIV-1 RNA/ml). However, latent HIV-1 persists in resting CD4؉ T cells, and low residual levels of free virus are found in the plasma. Limited characterization of this residual viremia has been done because of the low number of virions per sample. Using intensive sampling, we analyzed residual viremia and compared these viruses to latent proviruses in resting CD4 ؉ T cells in peripheral blood. For each patient, we found some viruses in the plasma that were identical to viruses in resting CD4 ؉ T cells by pol gene sequencing. However, in a majority of patients, the most common viruses in the plasma were rarely found in resting CD4 ؉ T cells even when the resting cell compartment was analyzed with assays that detect replication-competent viruses. Despite the large diversity of pol sequences in resting CD4 ؉ T cells, the residual viremia was dominated by a homogeneous population of viruses with identical pol sequences. In the most extensively studied case, a predominant plasma sequence was also found in analysis of the env gene, and linkage by long-distance reverse transcriptase PCR established that these predominant plasma sequences represented a single predominant plasma virus clone. The predominant plasma clones were released for months to years without evident sequence change. Thus, in some patients on antiretroviral therapy, the major mechanism for residual viremia involves prolonged production of a small number of viral clones without evident evolution, possibly by cells other than circulating CD4 ؉ T cells.Treatment of human immunodeficiency virus type 1 (HIV-1) infection with highly active antiretroviral therapy (HAART) reduces viremia to below the detection limit of ultrasensitive clinical assays (15,16,37). However, HIV-1 persists in resting CD4 ϩ T cells (6,8,9,12,51) and possibly other reservoirs (4, 58). The latent reservoir in resting CD4ϩ T cells has a long half-life (11,41,44,47,56) that will likely preclude virus eradication unless novel approaches (5, 24-28, 42) can purge latently infected cells.In patients on HAART, HIV-1 persistence is evidenced not only by the latent reservoir in resting CD4 ϩ T cells but also by free virus in the plasma (10,17,19,36,41,48,52). Free virions can be found with special methods, even in patients who do not have clinically detectable viremia (10,18,19,36,52). Given the short half-life of free virus (20,49), this residual viremia indicates active virus production. This virus production may reflect low-level ongoing replication that continues despite HAART (7,10,13,14,18,21,33,48,56) and/or release of virus from latently infected cells that become activated (19,22,34,48,55) or from other stable cellular reservoirs (4, 58). The characterization of residual viremia may provide a means for determining the importance of different mechanisms of viral persistence.Although the presence of free virus can be detected ...

The Hippo tumor suppressor pathway restricts tissue growth by inactivating the transcriptional coactivator Yki. Although Sd has been implicated as a DNA-binding transcription factor partner for Yki and can genetically account for gain-of-function Yki phenotypes, how Yki regulates normal tissue growth remains a long-standing puzzle since Sd, unlike Yki, is dispensable for normal growth in most Drosophila tissues. Here we show that the yki mutant phenotypes in multiple developmental contexts are rescued by inactivation of Sd, suggesting that Sd functions as a default repressor and that Yki promotes normal tissue growth by relieving Sd-mediated default repression. We further identify Tgi as a cofactor involved in Sd's default repressor function and demonstrate that the mammalian orthologue of Tgi potently suppresses the YAP oncoprotein in transgenic mice. These findings fill a major gap in Hippo-mediated transcriptional regulation and open up new possibilities for modulating the YAP oncoprotein in cancer and regenerative medicine.