Functional domains of Lnk critical for cell-growth regulation. (A) Schematic representations of Lnk mutants and the pMY vector used for coexpressing Lnk mutants and eGFP from a single mRNA carrying an IRES. The N-terminal domain with its proline-rich stretches (▪), the PH domain (), the SH2 domain (□), and a tyrosine phosphorylation site at the C terminus (Y) are illustrated. Deletions of the N-terminal domain (dN), the PH domain (dPH), and the C-terminal tail (dC) as well as substitutions for Y536 by phenylalanine (Y536F) and R364 by glutamic acid (R364E; depicted as “X” in the SH2 domain) are indicated. (B) MC9 cells transduced with a control vector (left column, “vector”) or a Lnk-expressing vector (right column, “WT”) were cultured in the presence of SCF, and the percentages of live eGFP-positive cells were determined by flow cytometry at the indicated time points. (C) SCF-induced growth rates of MC9 cells expressing the indicated Lnk mutants were compared with that of nontransduced cells by dividing the percentage of eGFP-positive cells at each indicated time point by that at the start of culture (day 0). Data represent means ± SD of at least 3 experiments.