Serine Residues 726 and 780 Have Nonredundant Roles Regulating STAT5a Activity in Luminal Breast Cancer

Phosphorylation of S726-, S780-, and Y694-STAT5a in response to prolactin in MCF7 luminal breast cancer cells was investigated with STAT5a knockdown and rescued with Y694F-, S726A-, or S780A-STAT5a, where the phospho-sites were mutated.