Nuclear envelope glycoprotein with poly(A)polymerase activity of rat liver: isolation, characterization, and immunohistochemical localization

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Abstract
A protein with poly(A) polymerase activity has been identified and isolated from hepatic nuclear envelopes of rats to near homogeneity. The ability of the enzyme to bind to concanavalin A-agarose and to be eluted from the column with methyl .alpha.-D-mannopyranoside (0.2 M) as well as the inhibitory effects of .alpha.-mannosidase suggested that it was a glycoprotein. Poly(A) polymerase has an absolute requirement for a divalent cation, ATP, and an oligonucleotide primer. The enzyme activity with Mn2+ was about 20-fold higher than that Mg2+. Several known inhibitors adversely affected poly(A) polymerase activity. The enzyme has a molecular weight of 64000 when analyzed by polyacrylamide gel electrophoresis under denaturing conditions and has a sedimentation coefficient of 4.5 S. Immunohistochemical studies using polyclonal antibodies raised against the purified enzyme revealed that the antigen was localized in the nuclear membranes.