RASA1（RAS p21 protein activator 1），癌症关联基因，基因ID：5921，该基因编码的蛋白质位于细胞质中，是GTP酶激活蛋白GAP1家族的一部分。基因产物刺激正常ras p21的GTPase活性，但不刺激其致癌对应物。作为ras功能的抑制因子，该蛋白增强ras蛋白微弱的内在GTPase活性，导致ras的非活性GDP结合形式，从而控制细胞增殖和分化。导致两种蛋白结合位点改变的突变与基底细胞癌有关。突变也与遗传性毛细血管畸形（CM）和动静脉畸形（AVM）及帕克斯-韦伯综合征有关。选择性剪接产生两种亚型，其中较短的亚型缺乏N端疏水区，但保持相同的活性，似乎在胎盘而不是成人组织中大量表达。The protein encoded by this gene is located in the cytoplasm and is part of the GAP1 family of GTPase-activating proteins. The gene product stimulates the GTPase activity of normal RAS p21 but not its oncogenic counterpart. Acting as a suppressor of RAS function， the protein enhances the weak intrinsic GTPase activity of RAS proteins resulting in the inactive GDP-bound form of RAS， thereby allowing control of cellular proliferation and differentiation. Mutations leading to changes in the binding sites of either protein are associated with basal cell carcinomas. Mutations also have been associated with hereditary capillary malformati。