Post-Transcriptional Regulation of the Gonadotropin-Releasing Hormone Gene in GT1–7 Cells
GT1–7 cells respond to treatment with the phorbol ester, phorbol 12-myristate 13-acetate (PMA), with an inhibition of transcription of the proGnRH gene and decreases in GnRH mRNA levels. However, the timing of this decrease in GnRH mRNA levels suggests that a decrease in GnRH mRNA stability may be involved in addition to an inhibition of transcription of the proGnRH gene. To address this possibility, we treated GT1–7 cells with 100 nM PMA for 4 h and then monitored GnRH mRNA levels over time after blockade of GnRH gene transcription with DRB. PMA treatment caused GnRH mRNA half-life to decrease from 30 to 11 h. Then, to verify this observation, we examined changes in GnRH mRNA poly (A) tail length, which may be a reflection of mRNA turnover, following treatment of GT1–7 cells with PMA or vehicle for 0, 4, 8 or 24 h. The poly (A) tail was removed from half of the GT1 cytoplasmic RNA sample by digestion with RNase H and the difference in GnRH mRNA size with and without RNase H treatment was determined by Northern hybridization. PMA treatment (4 and 8 h) resulted in a significant decrease in the length of the GnRH mRNA poly (A) tail, consistent with a decrease in GnRH mRNA stability. This finding suggests that GnRH mRNA turnover is inducible by substances such as PMA. Our study indicates that a change in mRNA stability is one of a multiplicity of levels at which GnRH gene expression is regulated.
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Document Type: Research Article
Affiliations: Fishberg Research Center for Neurobiology, Mount Sinai School of Medicine, PO Box 1065, New York, NY 10029, USA.
Publication date: 01 April 1997