Fig. 6. RSL1D1 interacts with the B- and G-domains of nucleostemin. (A) Schematic diagrams of truncated nucleostemin mutants used to determine RSL1D1-interacting domain(s). (B) Affinity binding assays showing that GST fusions of RSL1D1 are able to pull down all single-domain deletion mutants of nucleostemin, suggesting involvement of multiple regions. (C) The use of truncation mutants showed that RSL1D1 binds both the BC- and the GI-domains, but not the G- and IA-domains or a GI-domain containing a G256V mutation (GI(256)). (D) Nucleostemin RSL1D1-binding domains were further narrowed down to the B-domain of the BC mutant (D1) and the GI1-domain of the GI mutant (D2). Double-deletion mutants (NSdBG and NSdCI) confirmed the importance of the B- and G-domains, but not of the C- and I-domains, in mediating the interaction of nucleostemin and RSL1D1 (D2).