ARF mediates recruitment of PtdIns-4-OH kinase-beta and stimulates synthesis of PtdIns(4,5)P-2 on the Golgi complex

The small GTPase ADP-ribosylation factor (ARF) regulates the structure and function of the Golgi complex through mechanisms that are understood only i n part, and which include an ability to control the assembly of coat comple xes and phospholipase D (PLD), Here we describe a new property of ARF, the ability to recruit phosphatidylinositol-4-OH kinase-beta and a still uniden tified phosphatidylinositol-4-phosphate-5-OH kinase to the Golgi complex, r esulting in a potent stimulation of synthesis of phosphatidylinositol-4-pho sphate and phosphatidylinositol-4,5-bisphosphate; this ability is independe nt of its activities on coat proteins and PLD, Phosphatidylinositol-4-OH ki nase-beta is required for the structural integrity of the Golgi complex: tr ansfection of a dominant-negative mutant of the kinase markedly alters the organization of the organelle.