Abstract 3469: Identification of novel human telomerase associated protein by mass spectrometry

Abstract

Abstract Telomeres are nucleoprotein structures at the ends of eukaryotic chromosomes that prevent them from degradation, recombination, and end-to-end fusion. Telomere consists of DNA repeats, which in human is of the sequence TTAGGG, and it is bound by a group of proteins called shelterin complex. Telomere is synthesized by telomerase. Telomerase is absent in most human somatic cells while it is up-regulated in 90% of cancer cells, in which telomerase plays an essential role in cancer cells’ replicative immortality. However, telomerase is only present at approximately 250 molecules per cancer cell. To exert its function of elongating telomere, telomerase has to find the end of telomeres which needed to be elongated. However, how telomerase is precisely recruited to telomere ends is not clearly understood. To better understand the recruitment process of telomerase, we initially screened and subsequently identified novel binding proteins of hTERT, the catalytic subunit of telomerase, through a pull-down assay using cancer cell lines with endogenously Flag-tagged hTERT. Using mass spectrometry (MS), we were able to identify a promising interesting protein. Further, direct interaction between TERT and this protein was validated. Then, we found that this protein can also interact with the shelterin component, TRF1 (Telomeric repeat-binding factor 1), which binds to double stranded telomeric DNA. Furthermore, from previous published reports, this protein was shown to interact with single-stranded telomeric DNA binding protein POT1 (Protection of Telomeres 1) in the shelterin complex. Functionally, overexpression of this protein in cancer cell lines can result in the elongation of telomeres, while knock-down or knock-out of the protein results in the shortening of telomere. In conclusion, we identified an hTERT-binding protein that affects telomere maintenance which may be involved in telomerase recruitment process. In the long run, it could serve as a potential therapeutic target for cancers. Citation Format: Jing Wang, Xuezhi Bi, Shang Li. Identification of novel human telomerase associated protein by mass spectrometry [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3469. doi:10.1158/1538-7445.AM2017-3469