Regulation of erythroid cell-specific gene expression during erythropoiesis.

The aim of our group's work over the past few years has been to investigate the molecular mechanisms regulating erythroid cell-specific gene expression during erythroid cell differentiation. In addition to the alpha-globin gene, we have focussed on two non-globin genes of interest encoding the rabbit red cell-specific lipoxygenase (LOX) and the mouse glutathione peroxidase (GSHPX), an important seleno-enzyme responsible for protection against peroxide-damage. Characterisation of the GSHPX gene showed that the seleno-cysteine residue in the active site of the enzyme is encoded by UGA, which usually functions as a translation-termination codon. This novel finding has important implications regarding mRNA sequence context effects affecting codon recognition. The regulation of the GSHPX and red cell LOX genes has been investigated by functional transfection experiments. The 700 bp upstream of the GSHPX promoter seems to function equally well when linked to the bacterial chloramphenicol acetyl transferase (CAT) gene and transfected into mouse erythroid or fibroblast cell lines. However, the presence of tissue-specific DNase I hypersensitive sites (DHSS) in the 3' flanking region of the GSHPX gene suggests that such sites may be important in its regulation in the various cell types in which it is highly expressed, i.e., erythroid cells, liver and kidney. The transcription unit of the RBC LOX gene has also been defined and 5' and 3' flanking regions are being investigated for erythroid-specific regulatory elements: a region upstream of the LOX gene gives increased expression of a linked CAT gene when transfected into mouse erythroid cell lines compared to non-erythroid cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)