Analysis of linked human ε and γ transgenes:: Effect of locus control region hypersensitive sites 2 and 3 or a distal YY1 mutation on stage-specific expression patterns

Stage-specific expression of the human beta-like globin genes is controlled by interactions between regulatory elements near the individual genes and additional elements located upstream in the Locus Control Region (LCR), Elucidation of the mechanisms that govern these interactions could suggest strategies to reactivate fetal (gamma) or embryonic (epsilon) genes in individuals with severe hemoglobinopathies. This study extends an earlier analysis of a transgenic construct, HS3 epsilon gamma, testing: (A) the effect of substitution of HS2 for HS3 on stage-specific expression of the epsilon and gamma genes and, (B) the role of an evolutionarily conserved YY1 binding site in transcriptional regulation of the gamma gene, The data show that both HS3 epsilon gamma and HS2 epsilon gamma can individually support embryonic expression of epsilon and fetal expression of A gamma. Thus, the cis regulators of distinct expression patterns for epsilon and gamma are likely to reside near the genes, rather than in specific hypersensitive sites of the LCR, Alterations in A gamma expression patterns observed in transgenic lines carrying a construct with a mutation in a conserved YY1 binding site at -1086 indicate that this site might function to facilitate active transcription of the gamma gene in fetal life. (C) 1999 by The American Society of Hematology.