EN
STATs (signal transducers and activators of transcription) are latent transcription factors present in the cytoplasm of the majority of animal cells. They are activated by tyrosine phosphorylation and then translocated to the nucleus where they induce transcription of target genes. The STAT5A factor mediates the actions of cytokines and peptide hormones, including prolactin and growth hormone. STAT5A, previously known as MGF (mammary gland factor), is the most important transcription factor mediating the action of ligands on the expression of genes responsible for production traits in cattle.