Coupling of GnRH concentration and the GnRH receptor-activated gene program.
The initial waves of gene induction caused by GnRH in the LbetaT2 gonadotrope cell line have recently been identified using microarrays. We now investigate the relationship of the concentration of GnRH to the level of biosynthesis induced. Using an optimized custom cDNA microarray, we show that a large number of genes are induced in a concentration-dependent fashion. Detailed time course studies of the induction of six induced transcripts using quantitative real-time PCR suggest that the amplitude, but not the temporal pattern, depends on the concentration of GnRH. The early genes appear to show a delay in gene induction, followed by a linear phase of increase. The relationship of rate of synthesis and GnRH concentration was studied by mathematical modeling of the induction of two genes, gly96 and tis11. In both cases, only the rates of increase, but not the lag times, are influenced by the concentration of GnRH exposure. Western blot analyses for c-Jun and Egr1 show that the levels of nuclear protein for these transcription factors also depend on the concentration of GnRH. These studies indicate that, despite the complex signaling network connecting the receptor to the activated genes, the biosynthetic rate of RNA polymerase at induced genes is correlated with the concentration of GnRH at the GnRH receptor.
Yuen
Tony
T
Department of Neurology, Mount Sinai School of Medicine, New York, New York 10029, USA.
Wurmbach
Elisa
E
Ebersole
Barbara J
BJ
Ruf
Frederique
F
Pfeffer
Robert L
RL
Sealfon
Stuart C
SC
D015153:Blotting, Western; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D051766:Early Growth Response Protein 1; D005786:Gene Expression Regulation / Q000187:drug effects*; D007987:Gonadotropin-Releasing Hormone / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D017874:Immediate-Early Proteins; D007295:Inositol Phosphates / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D020411:Oligonucleotide Array Sequence Analysis; D011966:Receptors, LHRH / Q000235:genetics* / Q000378:metabolism*; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D017874:Immediate-Early Proteins; D007295:Inositol Phosphates; D011966:Receptors, LHRH; D014157:Transcription Factors; D007987:Gonadotropin-Releasing Hormone; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases