Expression and regulation of the beta-subunit of ovine follicle-stimulating hormone relies heavily on a promoter sequence likely to bind Smad-associated proteins.
FSH is essential for normal gonadal function in mammals. Expression of its beta-subunit (FSHB) controls overall production/secretion of FSH and is induced by activin. Studies with ovine FSHB promoter/reporter constructs in L beta T2 gonadotropes show that induction by activin requires a putative Smad binding element in the ovine FSHB promoter (-162AGAC-159). Similar studies reported here show that another site, juxtaposed to the Smad binding element, was also required for 81% activin induction in L beta T2 cells. This site was similar to several that bind proteins known to partner with Smads. When this site (-171ACTgcgtTT-163) was mutated by changing the nucleotides shown in lowercase letters, the resulting ovine-derived construct (mut-oFSHBLuc) was expressed poorly as a transgene in primary mouse gonadotropes (<0.001 times compared with ovine wild-type transgenes). This decrease in expression demonstrated the importance of this site for activin induction and, perhaps, basal expression, although studies with L beta T2 cells did not suggest this latter possibility. Expression of mut-oFSHBLuc in male mouse gonadotropes in vivo was at least 644 times greater than expression in all but one nongonadotrope tissue tested, indicating that mut-oFSHBLuc retained significant gonadotrope-specific expression. An increase in FSHB expression occurs during estrus in mice and is faithfully reproduced with wild-type ovine FSHBLuc transgenes, but not with mut-oFSHBLuc, indicating that the mutated site is needed for this secondary FSH surge. These data suggest that activin gathers Smads and Smad-associated proteins at the -171/-159 promoter region to regulate expression of the ovine FSHB and overall FSH production.
Su
Pei
P
Department of Molecular and Structural Biochemistry, Box 7622, North Carolina State University, Raleigh, North Carolina 27695-7622, USA.
Shafiee-Kermani
Farideh
F
Gore
A Jesse
AJ
Jia
Jingjing
J
Wu
Joyce C
JC
Miller
William L
WL
D000818:Animals; D005640:Follicle Stimulating Hormone / Q000235:genetics; D037201:Follicle Stimulating Hormone, beta Subunit / Q000235:genetics*; D005786:Gene Expression Regulation; D011401:Promoter Regions, Genetic; D012756:Sheep; D051785:Smad Proteins / Q000235:genetics*
D037201:Follicle Stimulating Hormone, beta Subunit; D051785:Smad Proteins; D005640:Follicle Stimulating Hormone