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V. R. Chavali, J. Sommer, R. M. Petters, R. Ayyagari; Identification of a Promoter for the Human CTRP5 Gene. Invest. Ophthalmol. Vis. Sci. 2009;50(13):479.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of this study was to identify the functional promoter sequence that regulates the expression of Complement-1q tumor necrosis factor-related protein 5 (CTRP5). The CTRP5 gene has been found in the 3' untranslated region of the Membrane Frizzled related protein (MFRP) gene and these two genes were predicted to be dicistronic partners. In this study we evaluated the 5' upstream sequence of CTRP5 for the presence of a promoter regulating the expression of this gene.
The sequence upstream to the translational start site of human CTRP5 (hCTRP5) was analyzed for the presence of a promoter region by Promoter Inspector software (Genomatix). An expression vector was constructed with the V5 tagged-pig CTRP5 (pCTRP5) gene downstream to a 1.3kb sequence from the region 5' to the human CTRP5. ARPE19 cells and CHO-KI cells were transfected using this construct and the promoter activity was tested by immunocytochemistry and western blot analysis. A series of promoter deletion constructs were produced utilizing the pGL3-Enhancer vector to characterize luciferase expression from 3.6kb- 380bp of the hCTRP5 putative promoter. CHO-KI cells were transiently transfected with these plasmids and luciferase activity was measured as a function of promoter activity.
Bioinformatic analysis of a 3.6 kb sequence from the upstream region of hCTRP5 resulted in the identification of a putative promoter region between nt -1293 and +1. Cells transfected with V5-tagged pCTRP5 downstream to the predicted CTRP5 promoter were able to express CTRP5 indicating that this promoter is functional. The promoter deletion constructs revealed that the sequence between nt-1293 to +1 is necessary for promoter activity. The 1.3 kb sequence of the hCTRP5 predicted promoter region produced higher levels of luciferase activity in CHO-KI cells when compared to the SV40 viral promoter indicating the higher strength of cloned CTRP5 promoter.
The present study is the first report revealing the presence of a functional promoter for the CTRP5 gene independent of MFRP and located 5' to its start site. Understanding the regulation of CTRP5 gene transcription may provide insights into the possible role of CTRP5 in causing LORD in patients. In addition these studies will also determine if the CTRP5 and MFRP are functionally dicistronic.
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