The Hippo pathway was discovered as a conserved tumour suppressor pathway restricting cell proliferation and apoptosis. However, the upstream signals that regulate the Hippo pathway in the context of organ size control and cancer prevention are largely unknown. Here, we report that glucose, the ubiquitous energy source used for ATP generation, regulates the Hippo pathway downstream effector YAP. We show that both the Hippo pathway and AMP-activated protein kinase (AMPK) were activated during glucose starvation, resulting in phosphorylation of YAP and contributing to its inactivation. We also identified glucose-transporter 3 (GLUT3) as a YAP-regulated gene involved in glucose metabolism. Together, these results demonstrate that glucose-mediated energy homeostasis is an upstream event involved in regulation of the Hippo pathway and, potentially, an oncogenic function of YAP in promoting glycolysis, thereby providing an exciting link between glucose metabolism and the Hippo pathway in tissue maintenance and cancer prevention.

Macrophages sense biophysical cues in the microenvironment via YAP to tune their inflammatory response.

In both Drosophila and mammalian systems, the Hippo pathway plays an important role in controlling organ size, mainly through its ability to regulate cell proliferation and apoptosis. The key component in the Hippo pathway is the Yes-associated protein YAP1, which localizes in nucleus, functions as a transcriptional coactivator, and regulates the expression of several proliferation- and apoptosis-related genes. The Hippo pathway negatively regulates YAP1 transcriptional activity by modulating its nuclear-cytoplasmic localization in a phosphorylation-dependent manner. Here, we describe the identification of several new PY motif-containing proteins, including angiomotin-like protein 1 (AMOTL1) and 2 (AMOTL2), as YAP1-associated proteins. We demonstrate that AMOTL1 and AMOTL2 can regulate YAP1 cytoplasm-to-nucleus translocation through direct protein-protein interaction, which can occur independent of YAP1 phosphorylation status. Moreover, down-regulation of AMOTL2 in MCF10A cells promotes epithelial-mesenchymal transition, a phenotype that is also observed in MCF10A cells with YAP1 overexpression. Together, these data support a new mechanism for YAP1 regulation, which is mediated via its direct interactions with angiomotin-like proteins.

BRCA1 promotes homologous recombination repair and antagonizes 53BP1-dependent nonhomologous end joining (NHEJ) pathway. However, the molecular basis of the competition between BRCA1 and 53BP1 pathways remains elusive. Here we report that RIF1 protein translocates to damage sites via ATM-dependent 53BP1 phosphorylation. Strikingly, loss of RIF1 rescues initial DNA end resection and checkpoint activation in BRCA1-depleted cells. Interestingly RIF1 accumulation at damage sites is antagonized by BRCA1 in S and G₂ phases. Conversely, the translocation of BRCA1 to damage sites is inhibited by RIF1 in G₁ phase. However, loss of RIF1 differs from that of 53BP1 deficiency, as it cannot fully rescue RAD51 foci formation, homologous recombination defect, and radio-hypersensitivity in BRCA1-deficient cells. This is likely because RIF1, but not 53BP1, also regulates the foci formation and chromatin loading of BLM (the Bloom syndrome helicase). Thus, RIF1 not only acts downstream of 53BP1 and counteracts BRCA1-mediated end resection but also has a secondary role in promoting BLM function in DNA repair.

Long non-coding RNAs (lncRNAs) have emerged as critical regulators in various cellular processes. However, the potential involvement of lncRNAs in kinase signalling remains largely unknown. AMP-activated protein kinase (AMPK) acts as a critical sensor of cellular energy status. Here we show that the lncRNA NBR2 (neighbour of BRCA1 gene 2) is induced by the LKB1–AMPK pathway under energy stress. On energy stress, NBR2 in turn interacts with AMPK and promotes AMPK kinase activity, thus forming a feed-forward loop to potentiate AMPK activation during energy stress. Depletion of NBR2 attenuates energy-stress-induced AMPK activation, resulting in unchecked cell cycling, altered apoptosis/autophagy response, and increased tumour development in vivo. NBR2 is downregulated and its low expression correlates with poor clinical outcomes in some human cancers. Together, the results of our study uncover a mechanism coupling lncRNAs with metabolic stress response, and provides a broad framework to understand further the regulation of kinase signalling by lncRNAs.

As the key effector in the Hippo pathway, YAP was identified as an oncoprotein whose expression is elevated in various human cancers. However, the development of potentially therapeutic compounds targeting YAP has been slow and limited. Here, we find that tankyrase inhibitors suppress YAP activity. This effect is mediated by anigomotin (AMOT) family proteins. Tankyrases associate with AMOT family proteins and promote their degradation through E3 ligase RNF146. By antagonizing tankyrase activity, tankyrase inhibitors stabilize AMOT family proteins, thereby suppressing YAP oncogenic functions. Together, our studies not only demonstrate the tankyrase-RNF146-AMOT axis as an upstream pathway regulating YAP but also reveal a therapeutic opportunity in targeting YAP for cancer treatment.