How is STAT5 recruited and activated in the JAK-STAT pathway?

• A. STAT5 is activated by receptor dimerization.
• B. STAT5 is recruited by binding to phosphorylated tyrosine residues on the cytokine receptor and activated by JAK2 phosphorylation.
• C. STAT5 is recruited by binding to unphosphorylated cytokine receptors.
• D. STAT5 is directly phosphorylated by the ligand.

Answer: (B)