The Role of Polycombs in the Stability of the Her2 Promoter G-Guadruplex
Authors:Veronica Magana, Veronica Magana, Luiza Nogaj, PhD
Mentor:Luiza Nogaj, PhD, Mount St. Mary's College
Chromosomal telomeres and some Guanine-rich gene promoters have the ability to form three dimensional structures known as G-quadruplexes. The formation of a G-quadruplex on a promoter prevents transcription factors from binding and silences gene expression from that promoter. c-myc and kit promoters, have been studied for the presence and nature of the G-quadruplex. Others, such as her2, have not been well characterized. Her2 protein overexpression plays an important role in development of breast cancer. Turning her2 promoter off could potentially slow this process and prevent breast cancer from progressing. We cloned 1000 bases upstream of the her2 gene start site and using GRS Mapper we identified 11 Quadruplex forming G-Rich Sequences in the her2 promoter. Using PCR, we biotinilated her2 promoter and bound magnetic streptavidin bead to the construct. To make the G-Quadruplexes, we incubated her2 promoter sequence at 90 degrees Celsius for 5 minutes and let it cool at room temperature for 2 hours. Biotinilated her2 promoter sequence was used in an immobilized template assay to check for Polycomb binding, known transcriptional silencers. Preliminary results suggest Polycomb binding in the presence of the quadruplex. Future work will focus on understanding the biochemical role of Polycomb in stabilizing her2 quadruplexes.