Transcriptional regulation in avian erythroid cells

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Abstract
Both the translational and transcriptional repertoires of nearly mature avian [chicken] erythroid cells appear to be highly restriced: molecular hybridization experiments demonstrate the presence of .apprx. 4000 spp. of poly(A)+ n[nascent]RNA and < 100 spp. of poly(A)+ mRNA. Whether the nRNA of erythroid cells contains sequences which, although not expressed in the erythroid cells, are found on polysomes in another cell type was determined. c[complementary]DNA was prepared from liver mRNA and the representation of liver mRNA sequences in the erythroid cell nRNA was determined. Liver mRNA consists of about 14,000 spp. Of poly(A)+ RNA. Of these only about 100 spp. are detectable in erythroid cell nRNA. The vast majority of liver mRNA species is undetectable in erythroid cells; i.e., they are present at less than 0.03 copies/cell. The few species of liver mRNA that are detectable in erythroid cells are present in both the nuclear and polysomal RNA at concentrations < 0.1 copies/cell. Gene expression in avian erythroid cells is apparently highly regulated at the transcriptional level.