In chicken leukemia cells globin genes are fully transcribed but their RNAs are retained in the perinucleolar area

Using hybridization in situ with a ribo-probe recognizing transcripts of th e chicken alpha A globin gene,, we show here that in proliferating AEV-tran sformed erythroblasts this gene is strongly transcribed, but the correspond ing transcripts are retained in the nuclei. Most surprisingly, this globin RNA accumulates in the perinucleolar areas in a pattern never observed befo re. Upon induction of cells to differentiate, leading to productive express ion of the hemoglobins, the transcripts of the alpha A globin gene were fou nd for the most part in the cytoplasm. In the nuclei of differentiated cell s, the globin RNA is concentrated in one or two specific spots, which are l ikely to represent the "processing centers" (PCs) of the globin RNA. The re sults presented indicate that posttranscriptional steps, of regulation invo lving in particular the perinuclear areas are of major importance for eryth roid differentiation. (C) 2001 Academic Press.