In vitro transcription of vitellogenin sequences on chick liver chromatin

The in vitro transcription of chick liver chromatin before and after estrogen treatment was studied. Transcription was by endogenous as well as homologous exogenous RNA polymerase II and the products were analyzed for size and specific vitellogenin sequences. Quantitatively more RNA was synthesized from chromatin of 24 h estrogen-treated (E 24) chicks than from that of untreated chicks. In either case the size of transcribed RNA ranged from 5S to larger than 28S and most was between 5S and 18S. When a fraction enriched in estrogen receptor (E-Rec) complex was added to chromatin from untreated chicks, a dramatic shift of the RNA transcribed into heavier regions occurred. Analysis of RNA transcripts by hybridization to cDNAvit showed an equal number of sequences transcribed from E 24 chromatin and control; however, 13 times more specific sequences were transcribed in the presence of E-Rec complex. The results indicate the E-Rec complex exerts a regulatory function in the specific transcription of the vitellogenin gene.