EFFECTS OF a-AMANITIN ON IN VITRO LABELING OF RNA FROM DEFINED NUCLEAR COMPONENTS IN SALIVARY GLAND CELLS FROM CHIRONOMUS TEN TANS

The effect of a-amanitin on nucleoside labeling of RNA in nucleoli, chromosomes, nuclear sap, and cytoplasm from Chironomus tentans salivary gland cells was investigated by radioautography and gel electrophoresis . Preribosomal RNA formation and processing in the nucleolus was not measurably influenced by the drug, and both 28 S and 18 S ribosomal RNA were transferred to the cytoplasm. In the chromosomes the heterogeneous RNA labeling was completely inhibited for the large size range (above 45-50 S) and partially for the low range . The labeling of 4-5 S chromosomal RNA was only moderately reduced. Most of the chromosomes showed radioautographically a disappearance of the normal band pattern, but some retained a pattern of weakly labeled bands . The electrophoretic results for the nuclear sap paralleled those for the chromosomes . The effect of a-amanitin on RNA labeling in these cells is similar but not identical to that of the substituted benzimidazole 5,6-dichloro-1 (/3-n-ribofuranosyl) benzimidazole (DRB) .