title: Poly(A) polymerase activity in ethionine-intoxicated rats: the relative effectiveness of disaggregated and intact polyribosomes as primers for poly(A) polymerase.
abstract: Ethionine intoxication causes a change in the metabolism of poly(A) sequences on the 3' OH terminus of mRNA in rat liver in vivo. In an attempt to determine the factors responsible for these changes, nuclear and cytoplasmic poly(A) polymerase activities and the state of the primer were examined in vitro. Requirements for optimal enzyme activities were determined. The nuclear and cytoplasmic enzymes had different K+, Mn2+, and poly(A) primer optima. The levels of nuclear and cytoplasmic poly(A) polymerase activity were shown to decrease following ethionine intoxication. Poly(A)+ RNA isolated from the livers of saline- and ethionine-treated rats served equally well as primers for the cytoplasmic poly(A) polymerase. Disaggregated polysomes were seven times more effective as primers than were intact polysomes. The results suggest that the mRNP particle which is released from polysomes as a result of ethionine intoxication functions better as a poly(A) polymerase primer than does the intact polysome.
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology; D003593:Cytoplasm / Q000201:enzymology; D004789:Enzyme Activation; D005001:Ethionine / Q000494:pharmacology*; D005260:Female; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D009713:Nucleotidyltransferases / Q000378:metabolism*; D011062:Polynucleotide Adenylyltransferase / Q000378:metabolism*; D011132:Polyribosomes / Q000201:enzymology*; D051381:Rats
chemical_list: D009713:Nucleotidyltransferases; D011062:Polynucleotide Adenylyltransferase; D005001:Ethionine