It has been demonstrated that K562 cells express epsilon- and gamma-globin genes but do not express beta-globin genes. The regulation of gene expression occurs at the level of transcription. We have set up a cell-free in vitro transcription system from K562 cells to determine the requirements for globin mRNA synthesis. As an initial attempt, we have prepared extracts from nuclei of both hemin-induced and uninduced K562 cells. The nuclear extracts could direct accurate transcription initiation in vitro from the epsilon-globin gene promoter without supplement with whole cell extracts. The results up to the present point to the existence of a globin gene expression regulatory factor(s) in K562 nuclear extracts. The in vitro transcription system will be used as an assay system for the isolation and characterization of such factors.
