Discipline: Biological Sciences
Subcategory: Cell and Molecular Biology
Manraj Gill - University of California at Berkeley
Co-Author(s): Kunitoshi Chiba and Dirk Hockemeyer, University of California at Berkeley, Berkeley, CA
Linear eukaryotic chromosomes have a repetitive DNA sequence at their ends, known as the telomere. The inability of DNA replication machinery to fully replicate the terminal regions of each chromosome results in loss of a portion of the telomere each cell division. Critically small telomeres serve as a signal to stop cellular replication. In this manner, telomeres serve as a buffer sequence to prevent loss of genetic information on the chromosomes. However, the telomerase enzyme can restore some lost telomeric sequence and increase the length of the telomere. In normal somatic cells, telomerase activity is absent because the transcription of the protein component of telomerase, TERT, is down regulated. However, cells with an unlimited potential to replicate, such as stem cells, maintain telomeres at a constant length by sustaining TERT expression. Moreover, 90% of cancer cells have high TERT expression that allows for continuous tumor growth. To study this down regulation of TERT upon differentiation and up regulation during tumor initiation, we focused on the endogenous TERT promoter. Using CRISPR/CAS9 mediated genome editing in human embryonic stem cells (hESCs), we engineered a variety of promoter deletions and cancer-associated mutations along with replacements of regulatory elements within this promoter. We found specific regions within the core promoter that are important for the expression of TERT in hESCs. We are currently generating mutations and smaller deletions in these regions to identify elements that could serve as a binding site for a repressor. These studies will help understand where and how the regulation of telomerase takes place.
Funder Acknowledgement(s): I was supported financially through a stipend from the Amgen Scholars Program at UC Berkeley over the summer of 2015.
Faculty Advisor: Dirk Hockemeyer,