Steroid Hormones Alter Telomerase Activity in 293T Cells

Abstract

Telomeres are nucleoprotein complexes that cap the ends of each strand of DNA in order to prevent the loss of genetic information during replication, protect the DNA from degradation, and inhibit chromosome fusion. During replication in most cells, telomeres shorten because of the end replication problem and continue to do so until they reach a critical length, resulting in cellular senescence. Telomere shortening is a natural process; however, individuals exposed to chronic stress have been observed to have shorter telomeres then those who have not. The biological significance and mechanism of stress-related telomere attrition are unclear. The aim of this work is to establish a model of stress-based alterations in telomerase (the ribonucleoprotein complex that replenishestelomeres) activity in 293T cells. The literature is unclear as to whether telomerase activity in these cells is regulated. Cells were exposed to physiological and supraphysiological levels of cortisol, estrogen, and testosterone. Utilizing FACS, the percent of cells in each phase of the cell cycle were quantified after stressing to correct telomerase activity by the amount of cells in S-phase, as telomeres are replenished in S-phase. Here, telomerase activity in 293T cells is shown to be partially regulated bypositive regulation of estrogen and testosterone. Negative regulation from cortisol appeared to be insignificant. cDNA was then prepared from testosterone trials in both 293T and Hff cells to compare hTERT expression, the catalytic subunit of telomerase. The prelimary qPCR results show conflicting trends in hTERT expression and this assay is ongoing. The positive regulation of 293T cells by stress can provide insights into the molecular basis of stress-induced telomere shortening through further study.