This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Boerboom, D. Articles by Sirois, J. Search for Related Content PubMed PubMed Citation Articles by Boerboom, D. Articles by Sirois, J.

Dual Regulation of Promoter II- and Promoter 1f-Derived Cytochrome P450 Aromatase Transcripts in Equine Granulosa Cells during Human Chorionic Gonadotropin-Induced Ovulation: A Novel Model for the Study of Aromatase Promoter Switching¹

Centre de Recherche en Reproduction Animale and Département de Biomédecine Vétérinaire, Faculté de Médecine Vétérinaire, Université de Montréal, Saint-Hyacinthe, Québec, Canada J2S 7C6

Address all correspondence and requests for reprints to: Dr. Jean Sirois, Faculté de Médecine Vétérinaire, Université de Montréal, C.P. 5000, Saint-Hyacinthe, Québec, Canada J2S 7C6. E-mail: siroisje{at}medvet.umontreal.ca

Estradiol biosynthesis is a key biochemical trait of developing follicles. To study its regulation in equine follicles, the objectives of this study were to clone and determine the structure of equine cytochrome P450 aromatase (P450AROM), and characterize the regulation of P450AROM and P450 17-hydroxylase/C17–20 lyase (P45017) messenger RNAs (mRNAs) in vivo in equine preovulatory follicles isolated during hCG-induced ovulation. Two distinct P450AROM complementary DNAs (cDNAs) were isolated from an equine preovulatory follicle cDNA library. One clone was 2682 bp in length and included 115 bp of 5'-untranslated region (UTR), 1509 bp of open reading frame encoding a well conserved 503-amino acid protein, and 1058 bp of 3'-UTR. Its 5'-most region represented the equine homolog of exon 1f, previously designated brain specific. The other cDNA clone encoded a truncated protein and contained a distinct 5'-UTR characteristic of transcripts derived from promoter II, previously identified as the predominant ovarian mRNA. Northern blot analyses were performed using preovulatory follicles obtained during estrus between 0–39 h after the administration of hCG and with corpora lutea isolated on day 8 of the estrous cycle (day 0 = day of ovulation). The results showed a biphasic regulation of P450AROM mRNA expression: levels were highest in follicles at 0 h post-hCG, decreased significantly during the ovulatory process at 12 and 24 h (P < 0.05), and increased again between 30–39 h post-hCG and in corpora lutea. When oligonucleotides specific for P450AROM mRNA variants were used as probes, a novel switching phenomenon was observed. Promoter II-derived transcripts accounted for the message present in follicles at 0 h post-hCG and in corpora lutea, whereas promoter 1f-derived mRNA was expressed exclusively during the ovulatory process (30–39 h post-hCG). Levels of P45017 mRNA were high in follicles at 0 h, but significantly decreased after hCG treatment (P < 0.05), with lowest levels in follicles at 36 and 39 h post-hCG and in corpora lutea. Northern blots performed on isolated cellular preparations revealed that P450AROM and P45017 transcripts were localized exclusively in granulosa cells and theca interna, respectively. Equine aromatase promoters II and 1f were cloned from a genomic library, and putative transcription start sites were characterized by primer extension assays. Sequence analyses identified distinct potential regulatory elements in each promoter. Thus, this study identifies a novel aromatase promoter-switching phenomenon in equine granulosa cells during follicular luteinization and provides a new model in which aromatase promoter switching is induced in vivo.

This article has been cited by other articles:

				K. Sayasith, N. Bouchard, M. Dore, and J. Sirois Cloning of equine prostaglandin dehydrogenase and its gonadotropin-dependent regulation in theca and mural granulosa cells of equine preovulatory follicles during the ovulatory process Reproduction, February 1, 2007; 133(2): 455 - 466. [Abstract] [Full Text] [PDF]

				K. A Brown, K. Sayasith, N. Bouchard, J. G Lussier, and J. Sirois Molecular cloning of equine 17{beta}-hydroxysteroid dehydrogenase type 1 and its downregulation during follicular luteinization in vivo J. Mol. Endocrinol., January 1, 2007; 38(1): 67 - 78. [Abstract] [Full Text] [PDF]

				K. Sayasith, M. Dore, and J. Sirois Molecular characterization of tumor necrosis {alpha}-induced protein 6 and its human chorionic gonadotropin-dependent induction in theca and mural granulosa cells of equine preovulatory follicles Reproduction, January 1, 2007; 133(1): 135 - 145. [Abstract] [Full Text] [PDF]

				K. A. Brown, M. Dore, J. G. Lussier, and J. Sirois Human Chorionic Gonadotropin-Dependent Up-Regulation of Genes Responsible for Estrogen Sulfoconjugation and Export in Granulosa Cells of Luteinizing Preovulatory Follicles Endocrinology, September 1, 2006; 147(9): 4222 - 4233. [Abstract] [Full Text] [PDF]

				K A Brown, D Boerboom, N Bouchard, M Dore, J G Lussier, and J Sirois Human chorionic gonadotropin-dependent induction of an equine aldo-keto reductase (AKR1C23) with 20{alpha}-hydroxysteroid dehydrogenase activity during follicular luteinization in vivo. J. Mol. Endocrinol., June 1, 2006; 36(3): 449 - 461. [Abstract] [Full Text] [PDF]

				K. Sayasith, N. Bouchard, D. Boerboom, K. A. Brown, M. Dore, and J. Sirois Molecular Characterization of Equine P-Selectin (CD62P) and Its Regulation in Ovarian Follicles During the Ovulatory Process Biol Reprod, March 1, 2005; 72(3): 736 - 744. [Abstract] [Full Text] [PDF]

				K. A. Brown, D. Boerboom, N. Bouchard, M. Dore, J. G. Lussier, and J. Sirois Human Chorionic Gonadotropin-Dependent Regulation of 17{beta}-Hydroxysteroid Dehydrogenase Type 4 in Preovulatory Follicles and Its Potential Role in Follicular Luteinization Endocrinology, April 1, 2004; 145(4): 1906 - 1915. [Abstract] [Full Text] [PDF]

				K. Golovine, M. Schwerin, and J. Vanselow Three Different Promoters Control Expression of the Aromatase Cytochrome P450 Gene (Cyp19) in Mouse Gonads and Brain Biol Reprod, March 1, 2003; 68(3): 978 - 984. [Abstract] [Full Text] [PDF]

				M. Kishida and G. V. Callard Distinct Cytochrome P450 Aromatase Isoforms in Zebrafish (Danio rerio) Brain and Ovary Are Differentially Programmed and Estrogen Regulated during Early Development Endocrinology, February 1, 2001; 142(2): 740 - 750. [Abstract] [Full Text] [PDF]

				D. Boerboom and J. Sirois Equine P450 Cholesterol Side-Chain Cleavage and 3{beta}-Hydroxysteroid Dehydrogenase/{{Delta}}5-{{Delta}}4 Isomerase: Molecular Cloning and Regulation of Their Messenger Ribonucleic Acids in Equine Follicles During the Ovulatory Process Biol Reprod, January 1, 2001; 64(1): 206 - 215. [Abstract] [Full Text]

				D. Boerboom, N. Pilon, R. Behdjani, D. W. Silversides, and J. Sirois Expression and Regulation of Transcripts Encoding Two Members of the NR5A Nuclear Receptor Subfamily of Orphan Nuclear Receptors, Steroidogenic Factor-1 and NR5A2, in Equine Ovarian Cells during the Ovulatory Process Endocrinology, December 1, 2000; 141(12): 4647 - 4656. [Abstract] [Full Text] [PDF]

				K. W. Walters, C. J. Corbin, G. B. Anderson, J. F. Roser, and A. J. Conley Tissue-Specific Localization of Cytochrome P450 Aromatase in the Equine Embryo by In Situ Hybridization and Immunocytochemistry Biol Reprod, May 1, 2000; 62(5): 1141 - 1145. [Abstract] [Full Text]