Large fragment of the probasin promoter targets high levels of transgene expression to the prostate of transgenic mice.
BACKGROUND
Androgen regulation and prostate-specific expression of targeted genes in transgenic mice can be controlled by a small DNA fragment of the probasin (PB) promoter (-426 to +28 base pairs, bp). Although the small PB fragment was sufficient to direct prostate-specific expression, the low levels of transgene expression suggested that important upstream regulatory sequences were missing.


METHODS
To enhance transgene expression, a large fragment of the PB promoter (LPB, -11,500 to +28 bp) was isolated, linked to the bacterial chloramphenicol acetyl transferase (CAT) gene, and microinjected into CD1 mouse oocytes to generate transgenic mouse lines.


RESULTS
As shown by the immunohistochemical studies, CAT gene expression was restricted to the prostatic epithelial cells in a tissue-specific manner. High levels of CAT gene expression were observed in two of the six LPB-CAT transgenic lines. In Line 1, developmental regulation of LPB-CAT was detected early, from 1 to 4 weeks of age, with the activity of CAT increasing from 3 to 40,936 dpm/min/mg protein. Upon sexual maturation and elevated serum androgen levels (7 weeks of age), a further 18-fold rise in CAT activity occurred. Hormone ablation by castration in mature mice dramatically reduced transgene expression, whereas treatment with androgens returned LPB-CAT expression to precastration levels. In contrast, treatment with glucocorticoids had no significant effect on CAT gene expression. Zinc treatment of the castrated animals also increased LPB-CAT expression three- to four-fold in two prostatic lobes.


CONCLUSIONS
This study demonstrates that important regulatory DNA sequences located in the LPB fragment contribute to tissue-specific expression and greatly increase levels of transgene expression induced by androgens and zinc.
Yan
Y
Y
Department of Urologic Surgery and Cell Biology, School of Medicine, Vanderbilt University, Nashville, Tennessee 37232-2765, USA.
Sheppard
P C
PC
Kasper
S
S
Lin
L
L
Hoare
S
S
Kapoor
A
A
Dodd
J G
JG
Duckworth
M L
ML
Matusik
R J
RJ
D000375:Aging / Q000378:metabolism*; D000727:Androgen-Binding Protein / Q000096:biosynthesis / Q000235:genetics*; D000818:Animals; D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis; D017931:DNA Primers; D003907:Dexamethasone / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000494:pharmacology; D004848:Epithelium / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D017930:Genes, Reporter; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009865:Oocytes / Q000502:physiology; D009919:Orchiectomy; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D011467:Prostate / Q000254:growth & development / Q000378:metabolism*; D051381:Rats; D011503:Transglutaminases / Q000096:biosynthesis / Q000235:genetics; D019287:Zinc Sulfate / Q000494:pharmacology
D000727:Androgen-Binding Protein; D017931:DNA Primers; C027519:probasin; D013196:Dihydrotestosterone; D019287:Zinc Sulfate; D003907:Dexamethasone; D015500:Chloramphenicol O-Acetyltransferase; D011503:Transglutaminases