Human beta-globin locus control region: analysis of the 5' DNase I hypersensitive site HS 2 in transgenic mice.
The human beta-globin locus control region (LCR) is essential for high-level expression of human epsilon-, gamma-, and beta-globin genes. Developmentally stable DNase I hypersensitive sites (designated HS) mark sequences within this region that are important for LCR activity. A 1.9-kilobase (kb) fragment containing the 5' HS 2 site enhances human beta-globin gene expression 100-fold in transgenic mice and also confers position-independent expression. To further define important sequences within this region, deletion mutations of the 1.9-kb fragment were introduced upstream of the human beta-globin gene, and the constructs were tested for activity in transgenic mice. Although enhancer activity was gradually lost with deletions of both 5' and 3' sequences, a 373-base-pair (bp) fragment retained the ability to confer relative position-independent expression. Three prominent DNase I footprints were observed in this region with extracts from the human erythroleukemia cell line K-562, one of which contained duplicated binding sites for transcription factor AP-1 (activator protein 1). When the 1.9-kb fragment containing an 18-bp deletion of the AP-1 binding sites was tested in transgenic mice, enhancer activity decreased 20-fold but position-independent expression was retained.
Caterina
J J
JJ
Department of Biochemistry, School of Medicine, University of Alabama, Birmingham 35294.
Ryan
T M
TM
Pawlik
K M
KM
Palmiter
R D
RD
Brinster
R L
RL
Behringer
R R
RR
Townes
T M
TM
D000818:Animals; D001483:Base Sequence; D003850:Deoxyribonuclease I; D005333:Fetus; D015870:Gene Expression; D005914:Globins / Q000235:genetics*; D006801:Humans; D008099:Liver / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009693:Nucleic Acid Hybridization; D009710:Nucleotide Mapping; D015345:Oligonucleotide Probes; D015183:Restriction Mapping
D015345:Oligonucleotide Probes; D005914:Globins; D003850:Deoxyribonuclease I