CAS nuclear localization involves its N-terminus. (A) CAS and Kapβ1 are asymmetrically partitioned in the nucleus and cytoplasm, respectively. Scale bar, 5 μm. (B) CAS structure adopted from Matsuura and Stewart (2004) (PDB ID: 1wa5, structure for the yeast homolog of CAS: CSE1Lp) and Cook et al. (2005) (PDB ID: 1z3h). Binding sites to RanGTP and Kapα such as HEATs 1–2 at the N-terminus (violet) and the C-loop (dark blue) are indicated. (C) Full-length CAS and truncation mutants used in this work. Binding sites for Kapα and RanGTP are indicated. (D) Immunostaining of Kapβ1 in cells expressing mCherry-CAS and associated truncation mutants. Scale bar, 5 μm. (E) N/C ratios reveal that mCherry-CAS, mCherry-CAS∆C, and mCherry-CAS∆Cloop are enriched in the nucleus but not mCherry-∆40NCAS, mCherry-∆40NCAS∆Cloop, mCherry-CASCloop, and mCherry-(1-40)NCAS. The dashed line indicates N/C = 1. Box plots denote the median, first, and third quartiles. The whiskers represent the minimum and maximum values. Number of independent experiments: N = 3. The data were tested for normality using a built-in function of GraphPad Prism software. P values were obtained using an unpaired two-tailed t test.