An Investigation of the Effects of the Core Protein Telomerase Reverse Transcriptase on Wnt Signaling in Breast Cancer Cells

Abstract

Telomerase canonically maintains telomeres, but recent reports have suggested that the core protein mammalian telomerase reverse transcriptase (TERT) component, together with the chromatin remodeling factor BRG1 and β-catenin, may also bind to and promote expression of Wnt target genes. However, this proposed noncanonical role of TERT in Wnt signaling has been controversial. Here, we investigated the effects of human TERT (hTERT) on Wnt signaling in human breast cancer lines and HeLa cells. We failed to find evidence for physical association of hTERT with BRG1 or β-catenin; instead, we present evidence that anti-FLAG antibody cross-reactivity properties may explain the previously reported interaction of hTERT with β-catenin. Furthermore, altering hTERT levels in four different breast cancer cell lines caused minimal and discordant effects on Wnt target and Wnt pathway gene expression. Although hTERT's role in Wnt signaling was addressed only indirectly, no significant representation of Wnt target genes was detected in chromatin immunoprecipitation-sequencing (ChIP-seq) and chromatin isolation by RNA purification and sequencing (ChIRP-seq) loci cooccupied in HeLa S3 cells by both BRG1 and hTR. In summary, our evidence fails to support the idea of a biologically consistent hTERT interaction with the Wnt pathway in human breast cancer cells, and any detectable influence of hTERT depended on cell type and experimental system.