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C.M. H. Colitz, C.A. Barden, H.L. Chandler, P. Lu; Ultraviolet Irradiation Up–Regulates Telomerase Transcription . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4082.
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We had previously shown that ultraviolet irradiation (UVR) significantly and maximally increases telomerase activity in canine lens epithelial cells at a dose of 600 J/m2 followed by a recovery period of 8 hours. However, we had not evaluated telomerase gene transcription. Therefore, we hypothesized that an acute dose of UVR followed by an 8 hour recovery period would up–regulate TERT, the catalytic subunit of telomerase, and possibly up–regulate TR, the RNA component of telomerase.
Six freshly harvested normal adult canine lenses per group were exposed to 0 or 600 J/m2 UVR, then allowed to recover for 8 or 24 hours prior to RNA extraction. Quantitative RT–PCR was performed using primers for canine TERT and TR, designed in our laboratory. A greater than two–fold difference was deemed physiologically relevant. Data is expressed as fold–difference and HPRT was used as the housekeeping gene.
Lenses exposed to UVR, then recovered for 8 hours had a 9.88 fold up–regulation of TERT while the lenses recovered for 24 hours had returned to normal unexposed levels of expression. Lenses exposed to UVR, then recovered for 8 hours had a 2.2 fold up–regulation of TR while the lenses recovered for 24 hours had returned to normal unexposed levels of expression.
Telomerase activity has been shown to be regulated at the transcriptional and post–translational levels in other telomerase positive cell types. Previous work in our laboratory showed dose, time and age–dependent changes in telomerase activity. The proposed hypothesis proved that TERT and TR transcription are up–regulated following an acute dose of UVR and 8 hours of recovery but by 24 hours, this effect has passed. TERT has an anti–apoptotic function and its up–regulation may be protecting LEC from the acute effects of UVR. We are continuing to evaluate the mechanisms by which telomerase is regulated in normal and cataractous LEC.
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