Estrogenic upregulation of DNA polymerase beta in oocytes of preovulatory ovine follicles

The basic premise of this investigation was that local hormonal control of stockpiling of the base excision repair polymerase (poly) beta within oocyt es of preovulatory follicles occurs as a function of cytoplasmic maturation . There was an increase in immunoreactive poly beta in sectioned oocytes of preovulatory ovine follicles during a 12-36-hour interval following the on set of prostaglandin (PG) F(2)alpha -induced (Day 14 of the estrous cycle) luteal regression; this response was not observed in subordinate (nonovulat ory) follicles. Accumulation of poly beta in oocytes at 36 hr after PGF(2)a lpha was negated by treatment of ewes at 12 hr with the aromatase inhibitor Arimidex or an ovulatory dose of GnRH (which, via surge gonadotropin stimu lation, acutely downregulates the proestrous rise in follicular estrogen bi osynthesis). Estradiol-17 beta stimulated poly beta expression (transcripti onal control) in oocytes of explanted (12 hr after PGF2a) follicles (24-hou r incubation). We suggest that a critical period of estrogen amplification in the preovulatory follicle underscores the capacity of its oocyte to effi ciently repair DNA and therefore reconcile spontaneous infidelities in geno mic integrity that inevitably occur during preimplantation embryogenesis. ( C) 2001 Wiiey-Liss, Inc.