Transcriptional Regulation by the Helix Bundle Peptide Hormones: Growth Hormone, Prolactin, and Hematopoietic Cytokines

Abstract

TODAY it is stylish to remark with fascination at the multiple overlapping functions of interleukins, colonystimulating factors, and a host of other “cytokines” that have been discovered in recent years. As a reminder that this is not really a new observation, the first HBP hormone to be purified was PRL (1), and it was recognized to have such a variety of biological actions that by 1963 there had been created a “vast and confusing literature” (2) replete with multiple names for the same hormone and arguments about how many hormones were responsible for each biological activity. The pleiotropy of PRL actions prompted Bern and Nicoll (3) to suggest in 1968 that it be renamed either “versatilin” or “omnipotin” (3), and by 1980 more than 200 actions of PRL had been documented in the various vertebrate classes (4). Redundancies between actions of PRL and GH were widely appreciated by the 1950s, and the similarities of human (h) PRL and hGH actions resulted in such controversies that many doubted the existence of separate human PRL and GHs until hPRL was definitively purified by Friesen's group in 1972 (5).