The Roles of 5′-HS2, 5′-HS3, and the γ-Globin TATA, CACCC, and Stage Selector Elements in Suppression of β-Globin Expression in Early Development

• Published in: The Journal of biological chemistry Vol. 274; no. 16; p. 11229
• Main Authors: Thanh Giang Sargent, Charles C. DuBois, Arlene M. Buller, Joyce A. Lloyd
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 16-04-1999
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.16.11229

The roles of HS2 and HS3 from the human β-globin locus control region and of the TATA, CACCC, and stage selector elements
of the γ-globin promoter, in competitive inhibition of β-globin gene expression in early development, were tested using stable
transfections of HEL and K562 cells. Cells with an HS3γβ construct demonstrate that HS3 exhibits enhancing activity, but compared
with HS2, this site participates less consistently in the inhibition of embryonic/fetal β-globin expression. In cells with
HS3HS2γβ constructs, the two HS sites act in concert to more effectively enhance γ-globin gene expression and to drive stage-specific
expression of the γ- and β-globin genes. A γ-globin gene with a –161 promoter can competitively inhibit β-globin gene expression.
HS3HS2γβ constructs were used to determine the effects of γ-globin promoter mutations within this region on competition. The
CACCC and TATA elements, but not the stage selector element, inhibit inappropriate embryonic/fetal stage expression of the
β-globin gene. The mutation in the γ-globin TATA element results in the use of two major alternative transcription start sites.
The data suggest that proteins binding to the γ-globin CACCC and TATA elements interact with those binding to HS2 and/or HS3
to preclude β-globin transcription in early development.