Phospholipase C digestion induces the removal of nuclear RNA: a cytochemical quantitative study

It has been reported that the incubation of isolated rat liver nuclear matrices with phospholipase C causes the digestion of the matrix-bound phospholipids and the release of most matrix-linked RNAs (Cocco et al., 1980). In this paper, the presence of phospholipids in nuclear substructures and the effects of their removal by phospholipase C digestion have been investigated by means of enzyme-colloidal gold cytochemistry. The nuclear phospholipids appear to be localized in the interchromatin areas and in the nucleolus and are virtually absent in the heterochromatin, when labelled with phospholipase C-colloidal gold. The double labelling test with ribonuclease A and phospholipase C conjugated with gold particles of different diameters shows that the nuclear phospholipids are co-localized with RNA-containing structures. The enzymatic digestion of phospholipids on thin sections of either isolated nuclei or pancreas embedded in LR White resin results in the decrease of the RNase-A colloidal gold labelling of nuclear RNA-containing structures, but not of the rough endoplasmic reticulum. The data confirm the presence of phospholipids in the nucleus in the absence of possible translocation due to isolation procedures and strengthen the hypothesis that they are involved in interactions between nucleic acids and proteins of the nuclear matrix.