Rac GTPase-activating protein 1 is an enzyme that in humans is encoded by the RACGAP1 gene. Rho GTPases control a variety of cellular processes. There are 3 subtypes of Rho GTPases in the Ras superfamily of small G proteins: RHO, RAC, and CDC42. GTPase-activating proteins (GAPs) bind activated forms of Rho GTPases and stimulate GTP hydrolysis. Through this catalytic function, Rho GAPs negatively regulate Rho-mediated signals. GAPs may also serve as effector molecules and play a role in signaling downstream of Rho and other Ras-like GTPases. Over-expression of RACGAP1 is observed in multiple human cancers including breast cancer, gastric cancer and colorectal cancer. Evidence show that RACGAP1 can modulate mitochondrial quality control by stimulating mitopahy and mitochondrial biogenesis in breast cancer. Knocking out RACGAP1 in vitro using CRISPR/Cas9 leads to cytokinesis failure.