Purification and properties of a nuclear exoribonuclease from Ehrlich ascites tumor cells.

Abstract

An exoribonuclease and an endoribonuclease were separated from Ehrlich ascites tumor and normal liver cell nuclear extracts. There is a marked preponderance of the exoribonuclease in the tumor nuclei and the endoribonuclease in the liver nuclei. The tumor exoribonuclease was extensively purified. It attacks nonhelical polyribonucleotides to produce 5''-mononucleotides; the enzyme appears to remain complexed with an individual polynucleotide molecule until it is almost totally degraded. Oligonucleotides are attacked from the 3''-OH end. The exoribonuclease may contribute to the relative deficiency of proteins in the tumor cell.