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 alpha D globin locus we used a nuclear runoff replication assay. Density labeling of nuclei showed that replication of the alpha D globin gene in normal and RSV-transformed CEF (RSV-CEF) is in the transcriptional direction. However, in RSV-CEF the signal from a specific restriction fragment between the alpha D and alpha A globin genes was lower in the replicated DNA. This decrease was selective in that the signal of this restriction fragment was not diminished in the unreplicated DNA in the same nuclei. When CEF transformed by temperature sensitive RSV were grown at the restrictive temperature for pp60src activity the loss of transformed cell morphology correlated with the reappearance of the replicated alpha globin 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 pp60src protein can activate transcription of the alpha D globin gene and change the replication of alpha globin chromatin.