A potential role for cell cycle control proteins in regulation of the cyclic adenosine 5'-monophosphate-responsive glycoprotein hormone alpha subunit gene.
The production of chorionic gonadotropin is coupled to the differentiation of the placenta. Expression of the alpha subunit of chorionic gonadotropin [glycoprotein hormone alpha (GPH-alpha)] is also known to be stimulated by treatment of placental cells with either cAMP or DNA synthesis inhibitors. Given these features, we used adenovirus E1A as a molecular probe to investigate a potential role for cell cycle regulatory proteins and kinases in the regulation of GPH-alpha expression. The E1A protein contains well-characterized domains that interact with a variety of cell cycle regulatory proteins. The E1A conserved regions 1 and 2 bind proteins that regulate cell cycle progression, including pRB, p107, and p130. The amino-terminal region of E1A binds several high molecular weight proteins and inhibits the transcriptional coactivator function of p300 and the homologous cAMP response element (CRE)-binding protein. We found that coexpression of E1A13S activated the GPH-alpha promoter, whereas E1A12S caused marked repression. Deletion mutants and point mutations revealed that repression by E1A12S required the CRE of the GPH-alpha promoter. Several distinct domains in E1A12S were necessary for maximal repression. A mutation of the E1A amino terminus (RG2), which inhibits binding of p300 and related high molecular weight proteins, reduced 12S repression by 40%. Mutation of the pocket protein-binding domains reduced repression by 20%, and mutations of both domains reduced repression by 80%. Overexpression of p300 or the pocket proteins (pRB, p130, and p107) induced GPH-alpha promoter activity 2-4-fold. Because the E1A amino terminus and pocket protein-binding domains together induce p34cdc2 kinase activity, the effect of p34cdc2 kinase expression on GPH-alpha activity was also assessed. Coexpression of p34cdc2 kinase or the activating p34cdc2 kinase mutant (T14AY15F) inhibited GPH-alpha promoter activity and acted through the CRE. We conclude that the GPH-alpha gene CRE is subject to regulation by cell cycle regulatory kinases and proteins.
Division of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Medical School, Chicago, Illinois 60611, USA.
R G
RG
Pestell
C
C
Albanese
R J
RJ
Lee
G
G
Watanabe
E
E
Moran
J
J
Johnson
J L
JL
Jameson
D000256:Adenoviridae; D002453:Cell Cycle; D002460:Cell Line; D006063:Chorionic Gonadotropin / Q000096:biosynthesis / Q000235:genetics*; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D005814:Genes, Viral; D005822:Genetic Vectors; D006801:Humans; D017354:Point Mutation; D011401:Promoter Regions, Genetic
D006063:Chorionic Gonadotropin; D016213:Cyclins; D000242:Cyclic AMP