EFFECT OF TRYPTOPHAN ON RAT HEPATIC NUCLEAR POLY(A)POLYMERASE ACTIVITY

Addition of poly(A) to hnRNA in the cell nucleus is a post-transcripti onal event and is presumed to be brought about by a specific poly(A)po lymerase. Since it is known that tryptophan rapidly increases the cyto plasmic levels of polyadenylated mRNA, it was of interest to investiga te whether the essential amino acid, tryptophan, affects the enzyme re sponsible for polyadenylation. Tryptophan (300 mg/kg body wt.) tube-fe d for 10 min elevated the hepatic nuclear enzymatic activities of both the chromatin-bound nuclear poly(A)polymerase (44%, n = 7) as well as that of the free solubilized form (48%, n = 7). Hepatic nuclear prote ins separated under denaturing conditions, transferred to nitrocellulo se sheets, and then probed with antibody raised against hepatic nuclea r poly(A)polymerase showed no differences between the hepatic nuclei o f control and tryptophan-treated rats.