Alteration of in vivo DNA synthesis in the alpha globin locus of chick embryo fibroblasts due to in vivo activity of Rous sarcoma virus pp60src

Globin gene transcription is activated in chick embryo fibroblasts (CEF) transformed by Rous sarcoma virus (RSV). To determine whether this activation is correlated with a change in the replication of the alphaD giobin locus we used a nuclear runoff replication assay. Density iabeiing of nuclei showed that repilcatlon of the aiphaD giobin gene in normai and RSV-transformed CEF (RSV-CEF) is in the transcrlptionai direction. However, in RSV-CEF the signai from a specific restriction fragment between the aiphaD and alphaA giobin genes was lower in the replicated DNA. This decrease was selective in that the signal of this restriction fragment was not diminished in the unrepiicated DNA In the same nuclei. When CEF transformed by temperature sensitive RSV were grown at the restrictive temperature for pp60arc activity the loss of transformed cell morphology correlated with the reappear ance of the replicated alpha giobin DNA fragments in their normal stoichiometry. By comparison, histone H5 gene expression was not seen in CEF or in RSV-CEF, and H5 gene replication was not perturbed by viral transformation. These results suggest that the viral pp60arc protein can activate transcription of the aiphaD giobin gene and change the replication of alpha giobln chromatin.