Regulation of signalling by receptor tyrosine kinases in HeLa cells involves the q-base.

The nutrition factor queuine (q; the q-base) is a modulator of mammalian cell proliferation: it can be inhibitory or stimulatory, depending on the metabolic state of the cell. The mechanism underlying this growth-modulating activity was investigated. It was found that the q-base acts antagonistic to epidermal growth factor (EGF) but synergistic with platelet-derived growth factor (PDGF) in HeLa cells. Binding of either growth factor to its receptor resulted in the activation of distinct cellular kinases. The activities of these kinases were profoundly affected by q. The results suggest that the q-base is involved in the homologous regulation of signalling by receptor tyrosine kinases.