Jak2 tyrosine kinase: a mediator of both housekeeping and ligand-dependent gene expression?
Jak2 is a nonreceptor tyrosine kinase that is essential for proper animal development and physiology. It is activated by ligand-occupied cell-surface receptors. Once activated, it then tyrosine phosphorylates the latent cytoplasmic transcription factors, termed the signal transducers and activators of transcription (STAT) proteins. Thus Jak2 is viewed as a classic mediator of ligand-dependent signal transduction. Recent studies, however, suggest that Jak2 may mediate cellular gene expression outside of the classically defined, ligand-activated, Jak/STAT-signaling paradigm. Here we review these studies, provide additional data, and discuss whether Jak2 is a mediator of ligand-independent gene transcription, and, in turn, whether our current understanding of the Jak/STAT signaling paradigm should be modified to incorporate these observations.
Wallace
Tiffany A
TA
Department of Physiology and Functional Genomics, University of Florida College of Medicine, Gainesville, FL, USA.
Sayeski
Peter P
PP
D000818:Animals; D005786:Gene Expression Regulation; D006801:Humans; D053614:Janus Kinase 2; D008024:Ligands; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D015398:Signal Transduction / Q000235:genetics; D014158:Transcription, Genetic
D008024:Ligands; D011518:Proto-Oncogene Proteins; D011505:Protein-Tyrosine Kinases; C507924:JAK2 protein, human; D053614:Janus Kinase 2