Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.27.1 (RNase)
 16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Chromatin phospholipidic fraction, as previously demonstrated, shows the same localization as RNA inside the nuclei. DNase and RNase treatment of nuclei removed almost totally the DNA, 63% of RNA and caused a 50% loss of phospholipids. The aim of the present investigation is to study the fraction of RNase undigested nuclear RNA and its relationship with the phospholipids still present in the nuclei. Isolated hepatocyte nuclei were treated with Triton X-100 and digested with RNase and DNase. The undigested nuclear material contained proteins (98%) and a small amount of RNA (1.7%), DNA (0.4%) and phospholipids (0.18%). The analysis of phospholipids showed the presence of two components only, namely phosphatidylcholine and sphingomyelin. In the same complex, the activity of sphingomyelin synthase, phosphatidylcholine-dependent phospholipase C and neutral sphingomyelinase has been detected. Treatment of isolated RNA with neutral sphingomyelinase modified the RNA in RNase sensitive RNA, thus suggesting that the SM may represent a bridge between two RNA strands possibly regulating transcription.
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PMID:Nuclear sphingomyelin protects RNA from RNase action. 971 60

After the first histochemical demonstration by Chayen and Gahan of the presence of phospholipids and especially of sphingomyelin in chromatin, this became the object of long debate and of contradictory results. The general conclusion was that the presence of phospholipids may due to contamination during the isolation of chromatin. More recently the existence of a phospholipid chromatin fraction was confirmed by demonstrating that isolated hepatocyte nuclei, labelled by saturated and unsaturated radioiodination method, showed the presence of radioactivity only in the membrane and not in the isolated chromatin. The phospholipid composition showed an enrichment in sphingomyelin which increased during hepatocyte maturation or erythroleukemic cell differentiation induced by DMSO. A decrease in sphingomyelin was observed at the beginning of the S-phase in regenerating liver or in cultured proliferating cells. These changes were due to the presence of sphingomyelinase and sphingomyelin synthase in the chromatin, the activity of which paralleled the variation in sphingomyelin content. The sphingomyelin was co-localized with RNA as shown by biochemical and electron microscopy methods. Using bromo-uridine it was demonstrated that labelled RNA and sphingomyelin were present in actively transcribing nuclear regions. Isolated nuclear complexes after DNase and RNase digestion contained not only protein, but also RNA and sphingomyelin. After hydrolysis of sphingomyelin the RNAse-resistant RNA becomes RNAse sensitive. It can therefore be concluded that sphingomyelin and the related enzymes are present in the chromatin; sphingomyelin may have a role in RNA transcription protecting RNA by RNAse digestion before its transfer to the cytoplasm.
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PMID:Chromatin-associated sphingomyelin: metabolism in relation to cell function. 1291 Apr 72