Abstract
Heterogeneous nuclear RNA HnRNA) was isolated from untreated and 5-bromodeoxyuridine (BrdUrd) treated hepatoma tissue culture (HTC) cells. analysis of this RNA by either electrophoresis on polyacrylamide-agarose gels or centrifugation in sucrose gradients demonstrated that BrdUrd caused a shift in the labeled HnRNA population toward a smaller size distribution. This effect was produced by concentrations of BrdUrd which specifically lower the level of the differentiated enzyme tyrosine aminotransferase, but do not greatly affect cell growth. Differential binding to oligo(dT) cellulose was used to fractionate HnRNA further into classes containing poly(A) (alpha), oligo(A) (beta) or neither category of A-rich sequences (gamma). BrdUrd did not alter the relative rates of uridine incorporation into the three classes. The shift in the labeled HnRNA population due to BrdUrd was observed in all three subclasses of HnRNA.