Abstract

AP1 transcription factors control rapid responses of mammalian cells to stimuli that impact proliferation, differentiation, and transformation. To determine which AP1 factors are present in and regulated by hormones in ovarian cells during specific stages of proliferation and differentiation, we used both in vitro and in vivo models, Western blotting, immunohistochemistry, DNA binding assays, and transfections of AP1 promoter-reporter constructs. The expression patterns of Jun and Fos family members in response to hormones (follicle-stimulating hormone (FSH), luteinizing hormone (LH), and cAMP) were distinct. JunB, c-Jun, c-Fos, and Fra2 were rapidly but transiently induced by FSH in immature granulosa cells. JunD and Fra2 were induced by LH and maintained as granulosa cells terminally differentiated into luteal cells. Forskolin and phorbol myristate acetate acted synergistically to enhance transcription of an AP1(-73COL)-luciferase construct. JunD appears to be one mediator of this effect, since JunD was a major component of the AP1-DNA binding complex in granulosa cells, and menin, a selective inhibitor of JunD, blocked transcription of -73COL-luciferase. Thus, FSH and LH via cAMP induce specific AP1 factors, the AP1 expression patterns are distinct, and that of JunD and Fra2 correlates with the transition of proliferating granulosa cells to terminally differentiated, non-dividing luteal cells.

Highlights

  • Growth of ovarian follicles involves regulated proliferation and differentiation of granulosa cells [1, 2]

  • Our initial goals were to determine which members of the AP1 family of transcription factors were present in undifferentiated granulosa cells and which factors might be regulated by hormones in association with proliferation versus differentiation

  • In proliferating granulosa cells of small follicles, induction by FSH of c-Jun, JunB, c-Fos, FosB, Fra1, and Fra2 is rapid but transient; the most dramatic increases occurred for JunB (16-fold) and Fra2 (11-fold)

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Summary

Introduction

Growth of ovarian follicles involves regulated proliferation and differentiation of granulosa cells [1, 2]. Cell extracts were prepared and analyzed by Western blotting using antibodies specific for individual members of the AP1 transcription factor family as follows: c-Jun, JunB, JunD, c-Fos, FosB, Fra1, and Fra2 (Fig. 2).

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