PHAS-I is a heat-stable protein (relative molecular mass approximate to 12,400) found in many tissues. It is rapidly phosphorylated in rat adipocytes incubated with insulin or growth factors. Nonphosphorylated PHAS-I bound to initiation factor 4E (eIF-4E) and inhibited protein synthesis. Serine-64 in PHAS-I was rapidly phosphorylated by mitogen-activated (MAP) kinase, the major insulin-stimulated PHAS-I kinase in adipocyte extracts. Results obtained with antibodies, immobilized PHAS-I, and a messenger RNA cap affinity resin indicated that PHAS-I did not bind eIF-4E when serine-64 was phosphorylated. Thus, PHAS-I may be a key mediator of the stimulation of protein synthesis by the diverse group of agents and stimuli that activate MAP kinase.
Lin, T-A., Kong, X., Haystead, T. A. J., Pause, A., Belsham, G., Sonenberg, N., & Lawrence, J. C. (1994). PHAS-1 as a link between mitogen-activated protein kinase and translation initiation. Science, 266(5185), 653-656. https://doi.org/10.1126/science.7939721