Serine phosphorylation of STATs

Tyrosine phosphorylation regulates the dimerization of STATs as an essentia l prerequisite for the establishment of a classical JAK-STAT signaling path . However, most vertebrate STATs contain a second phosphorylation site with in their C-termini, The phosphorylated residue in this case is a serine con tained within a P(M)SP motif, and in the majority of situations its mutatio n to alanine alters transcription factor activity. This review addresses re cent advances in understanding the regulation of STAT serine phosphorylatio n, as well as the kinases and other signal transducers implied in this proc ess. The biochemical and biological consequences of STAT serine phosphoryla tion are discussed.