Transcriptional regulation of human zeta and psi zeta globin genes.

The human psi zeta globin gene, although nearly identical in sequence to the functional zeta globin gene, does not produce detectable levels of mRNA in human erythroid cells that do produce high levels of zeta mRNA. This observed inactivity of the psi zeta gene is unlikely to be caused by mRNA instability since hybrid alpha/psi zeta gene constructs produce high levels of mRNA in Cos7 cell transient expression assays. The analysis of zeta and psi zeta gene constructs stably integrated into a zeta globin expressing cell line K562 demonstrates that exogenous zeta but not psi zeta genes are transcriptionally active. Furthermore the inactivity of the psi zeta is attributable to a negative sequence element adjacent to the promoter of the psi zeta gene.