REGULATION OF SIGNALING BY RECEPTOR TYROSINE KINASES IN HELA-CELLS INVOLVES THE Q-BASE

The nutrition factor queuine (q; the q-base) is a modulator of mammali an cell proliferation: it can be inhibitory or stimulatory, depending on the metabolic state of the cell. The mechanism underlying this grow th-modulating activity was investigated. It was found that the q-base acts antagonistic to epidermal growth factor (EGF) but synergistic wit h platelet-derived growth factor (PDGF) in HeLa cells. Binding of eith er growth factor to its receptor resulted in the activation of distinc t cellular kinases. The activities of these kinases were profoundly af fected by q. The results suggest that the q-base is involved in the ho mologous regulation of signalling by receptor tyrosine kinases. (C) 19 95 Academic Press, Inc.