Rat growth hormone gene expression. Both cell-specific and thyroid hormone response elements are required for thyroid hormone regulation.
The elements involved in mediating cell-specific and thyroid hormone stimulation of rat growth hormone gene expression have been defined by transfection studies and by nuclease footprinting. 5'-Flanking DNA extending to -104 can mediate cell-specific expression, and this is enhanced 3- to 4-fold with DNA extending to -145. Cell-specific factors, found only in rat growth hormone producing cells, bind within the -137/-107 and -95/-65 regions, and competition studies suggest that the same factor binds to both sites. The sequence A (A or T) TAAAT is found at the center of both footprints at -80 and -122, suggesting that it is a core component of the recognition sequence of the cell-specific factor. Disruption of the spatial and/or distance relationships between the two regions eliminates the enhanced level of cell-specific expression, suggesting a cooperative interaction of the proteins which bind to these elements. Sequences located between -208 and -178 can confer thyroid hormone-regulated expression when linked in either orientation in close proximity to one or both cell-specific elements. The thyroid hormone and cell-specific elements function as an enhancer-like unit and are both required to confer regulated expression to heterologous promoters. We propose that thyroid hormone acts via its receptor to enhance the function of the cell-specific element by forming a more "active" transcription complex which stimulates the level of gene expression.
Ye
Z S
ZS
Department of Medicine, New York University Medical Center, New York 10016.
Forman
B M
BM
Aranda
A
A
Pascual
A
A
Park
H Y
HY
Casanova
J
J
Samuels
H H
HH
D000818:Animals; D001358:Avian Sarcoma Viruses / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000378:metabolism; D003850:Deoxyribonuclease I / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005090:Exodeoxyribonucleases / Q000378:metabolism; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000235:genetics*; D011401:Promoter Regions, Genetic; D051381:Rats; D013329:Structure-Activity Relationship; D013963:Thyroid Hormones / Q000494:pharmacology / Q000502:physiology*; D014162:Transfection
D013963:Thyroid Hormones; D013006:Growth Hormone; D004247:DNA; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; D003850:Deoxyribonuclease I