Cysteine-rich protein 2 (CRP2) is a cofactor for smooth muscle cell (SMC) differentiation. Here, we examined the mechanism of CRP2 distribution dynamics during SMC differentiation. CRP2 protein directly associated with F-actin through its N-terminal LIM domain and Gly-rich region, as determined by ELISA. In undifferentiated cells that contain few actin stress fibers, CRP2 was broadly distributed throughout the whole cell, including the nucleus. After induction of SMC differentiation, CRP2 localized to actin stress fibers as they formed. The stress fiber-localized CRP2 entered the nucleus because of induced actin depolymerization. These CRP2 dynamics were reproduced by in silico simulation. CRP2 localization dynamics, which affect CRP2 function, are regulated by the formation of actin stress fibers in conjunction with SMC differentiation. (C) 2011 Elsevier Inc. All rights reserved.