encoding p190A RhoGAP is a cancer-associated gene with a mutation spectrum suggestive of a tumor-suppressor function. all tumors and thus ranks among the top 30 most significantly mutated genes in human cancer. This discovery was surprising because was the only gene with such high frequency of mutations that was not included in the Cancer Gene Census at that time. The mutation rate of is particularly high in uterine corpus endometrioid carcinoma, and the gene is also frequently mutated in squamous cell carcinoma and adenocarcinoma of the lung, head and neck cancer, and renal cell carcinoma (Kandoth et al., 2013; Lawrence et al., 2014). In addition, is located in a region of chromosome 19 that is focally deleted in numerous carcinomas (Zack et al., 2013). encodes p190A RhoGAP (p190A), a major GTPase-activating protein (GAP) for Rho family proteins (Settleman et al., 1992). p190A exhibits 50% sequence identity and the same overall structure as p190B RhoGAP (p190B), which is encoded by (Burbelo et al., 1995). Both p190A and p190B are widely coexpressed, and each is essential for normal mouse development and tissue homeostasis (Brouns et al., 2000; Sordella et al., 2002). p190A and p190B provide spatial and temporal control of Rho activity in response to extracellular signaling (Burbelo et al., 1995; Nakahara et al., 1998; Wildenberg et al., 2006). In this capacity, p190A and p190B order MK-2866 exert profound effects on the actin cytoskeleton and cellular processes directly dependent on actin polymerization. In addition, p190A and p190B have been shown to regulate transcriptional responses through TFII-I order MK-2866 and CREB, respectively (Sordella et al., 2002; Jiang et al., 2005). Cancer genome sequencing data support a tumor-suppressor role for (Kandoth et al., 2013; Lawrence et al., 2014). However, cellular functions of p190A consistent with such a role have not been determined. p190A plays pivotal roles in proliferative and motile capacities of mammalian cells, but the effects are not consistent with a tumor-suppressor role. Inhibition of p190A function by order MK-2866 knockdown or overexpression of GAP-deficient p190A inhibits cell spreading and protrusion, resulting in loss of cell polarity and perturbation of cell migration (Arthur and Burridge, 2001). A recent publication by Binam et al. (2016) confirms that p190A is required for directional cell motility and that order MK-2866 certain p190A mutations found in human cancer perturb directional cell motility. However, loss of directional motility is not a hallmark of cancer (Hanahan and Weinberg, 2011). A role for p190A in cytokinesis has also been established (Su et al., 2003). Overexpression of p190A perturbs cytokinesis, resulting in the emergence of multinucleate cells, and loss of p190A might therefore seem advantageous to cancerous cells. However, endogenous levels of p190A do not affect cytokinesis (Su et al., 2009). Moreover, depletion of p190A inhibits entry into the cell cycle, thereby perturbing cell proliferation (Su et al., 2009). Collectively, the published effects on proliferative and motile capacities associated with loss Sema3g of p190A function are not consistent with a tumor-suppressor role. In contrast, we demonstrate in this study that p190A promotes contact inhibition of cell proliferation (CIP). Loss of CIP represents one of the earliest appreciated hallmarks of cancer (Hanahan and Weinberg, 2011). This effect of p190A is shared with p190B. Next, using an unbiased approach, we show that p190A and p190B suppress the transcriptional activity of YAP, an effector of the Hippo pathway and an established modulator of CIP (Zeng and Hong, 2008; McClatchey and Yap, 2012; Gumbiner and Kim, 2014). We show that.