Use of an In Vitro Reporter Assay System to Validate the Association Between Promoter Methylation and Telomere Length

Abstract

Telomeres are repetitive non-coding sequences found at the ends of chromosomes involved in protecting the genome that can serve as a biomarker of a cell’s chronological age. While research on the mechanisms underlying telomere maintenance is still underway, recent studies have demonstrated a direct relationship between telomere length and overall health, and that individuals who experience excessive and chronic stress may have shorter telomeres than unstressed individuals. To better understand the mechanisms involved in telomere length homeostasis, we postulate that epigenetic processes play an important role in regulating telomere length, in particular by altering the activity of telomerase, an enzyme that adds telomeric repeats to the ends of chromosomes. Few studies have examined the relationship between DNA methylation, the addition of a methyl group to a cytosine preceding a guanosine, and telomere length. Thus, the aim of the present study was to elucidate the process by which genes involved in telomere maintenance may be epigenetically modified in response to stressors. Using data from the Fragile Families and Child Wellbeing Study, which provides a longitudinal analysis of methylation profiles and telomere lengths in advantaged and disadvantaged populations, we identified two genes, SOX3 and MAD1L1, whose promoters were differentially methylated in response to stress and significantly correlated with telomere length. By establishing an in vitro functional assay, we tested the effects of DNA methylation on downstream transcription and found that increased methylation attenuated gene expression. Future directions include validating the results of the functional assay to lay the groundwork for further analysis of candidate promoter regions, as well as other gene regulatory elements and forms of epigenetic regulation. In addition, we hope to further unpack the biological effects of stress by treating cells with cortisol, a key player in the stress response, and observing changes in the expression of SOX3, MAD1L1, and telomerase.