RCC2 (regulator of chromosome 1 2) is a multifunctional protein that plays critical roles in cell cycle regulation and small GTPase signaling. During mitosis, RCC2 is required for proper chromosome 1 by ensuring normal levels of MAD2L1, AURKB, and BIRC5 at inner centromeres and facilitating kinetochore-spindle attachment 1. The protein functions as a guanine nucleotide exchange factor (GEF) for RALA and negatively regulates RAC1 activity, thereby controlling cytoskeletal organization and cell migration 2. In cancer contexts, RCC2 exhibits oncogenic properties across multiple tumor types. It promotes proliferation and metastasis in gastric cancer through RalA activation and MAPK/JNK pathway modulation 2, while in prostate cancer, it cooperates with CD24 to regulate vimentin ubiquitination and β-catenin signaling 3. RCC2 is subject to post-translational modifications including lactylation at K124, which stabilizes MAD2L1 mRNA in breast cancer under high glucose conditions 1. The protein also participates in bacterial blood-brain barrier penetration by forming complexes with RalA and exocyst components 4. Clinically, RCC2 overexpression correlates with poor prognosis in various cancers, making it a potential therapeutic target 56.