Journal of Korean Endocrine Society 1994;10(3):200-213.
Published online November 6, 2019.
Identification of TPA - Response Element (TRE) in the Rat Thyrotropin - Releasing Hormone (TRH) Gene.
Woon Won Jung, Young Kil Choi, In Myung Yang, Kwang Sik Seo, Jeong Taek Woo, Sung Woon Kim, Jin Woo Kim, Young Seol Kim, Young Kil Choi, Seung Joon Park
There are two potential imperfect copies of the TRE consensus sequence between -47 and -113bp position on 5' upstream of the rat TRH gene. The upstream element(5'-TGcCgTCA-3') is located between -101 bp and -94 bp, and the downstream element(5'-TGAcCTCA-3') is positioned between -59bp and -52bp relative to the stranscription start site. The downstream variant differs from the consensus sequence of TRE(AP-1)(5'-TGACTCA-3'), by addition of one nucleotide. As there is no direct evidence that TPA stimulates the transcription of rat TRH gene, and there is no study to define TRE of the rat TRH gene, we performed Northern blot assay, transient gene expression study and gel shift assay to identify TRE. TRH mRNA expression of CA77 cells was increased about 2-2.5 fold 30 min after TPA stimulation. When PC12 cells were stimulated by TPA after transfection of the plasmids containing serially deleted 5'upstream of the rat TRH gene ligated to luciferase gene, the transcription of luciferase gene was increased more than 3.2 fold with the plasmid pTRH(-600/84)Luc and pTRH(-113/84)Luc. However, the transcriptional activation was remarkably decreased less than 1.6 fold with pTRH(-77/84)Luc, pTRH(-47/84)Luc, and pTRH(6/84)Luc. The plasmid containing the sequence of -108/-79 did not show any significant activation in both of basal and TPA-stimulated transcription, whereas the plasmid containing the sequence of -70/-41 showed a slight but significant transcriptional activation by TPA. The plasmid containing the sequence of -114/-47 showed remarkable increase in basal transcription and TPA induced transcription of luciferase gene. Gel shift assay revealed that the oligonucleotides spanning -108/-79 and -70/-41 bound to c-Jun, whereas the oligonucleotides spanning -40/1, 1/30, 31/60, 61/84 did not bind. The oligonucleotide of -70/-41 bound to c-Jun with higher affinity compared to that of -108/-79. The one base pair mutant of -70/-41(deletion of C from the middle of TGACCTCA) bound to c-Jun with higher affinity, whereas the one base pair replaced mutant(C to G) bound with lower affinity compared to the wild type oligonucleotide. These results suggest that the rat TRH gene expression is stimulated by TPA to a smaller degree compared to that of other genes, and the two elements act cooperatively as TRE. The downstream TRE variant is mainly responsible for TPA response and c-Jun binding, and the upstream variant play a permissive role for transcriptional activation. The addition of one nucleotide C in the downstream element may be responsible for the relatively lower response of the rat TRH gene to TPA.
Key Words: Thyrotropin - releasing hormone (TRH), TPA

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