Lipid phosphorylation in isolated rat liver nuclei Synthesis of polyphosphoinositides at subnuclear level

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Abstract
Isolated rat liver nuclei and subnuclear fractions synthesize polyphosphoinositides in vitro in a mode dependent on the presence of nuclear membrane, detergent and exogenous substrates. The nuclear membrane is not essential as a source of lipid kinases, since the addition of erogenous phosphatidylinositol or phosphatidylinositol monophosphate to reaction mixtures lacking membranes restores the synthesis of phosphatidylinositol mono‐ and bisphosphate, respectively. Inositide phosphorylation is best accomplished by high‐salt extracted nuclei and pre‐detergent lamina. These data suggest that the nucleus, and especially the nuclear periphery, is a cell compartment in which polyphosphoinositide synthesis occurs; this might be related to the progression of phosphatidylinositol metabolism‐dependent signals to the genetic apparatus.