Resolution of telomeric nucleotide structure barriers by specific structure nucleases

National Institute On Aging

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Abstract

We have characterized the role of an RNA binding protein, WY2, in telomere protection in a subset of human malignancies that use the alternative lengthening of telomeres (ALT), a homology-directed telomere maintenance process. Telomeres in ALT cells exhibit an inherent susceptibility to replication stress. Our findings show that ALT cells are substantially enriched for WY2, especially under replication stress. Our ongoing efforts aim to examine the molecular basis of WY2 in telomere integrity protection by using ALT cells depleted of WY2 or expressing particular WY2 disruption. Balanced levels of telomeric repeat containing RNA (TERRA) and its formation of RNA:DNA hybrid (or R-loop) have an impact on telomere maintenance, especially in ALT cancer cells. We found that WY2 was a TERRA binding protein as well as a novel regulator of telomeric R-loop formation. WY2 inhibits the expression of TERRA. It also suppresses the formation of telomeric R-loops by binding to TERRA. WY2 deficiency causes a number of consequences, including increased TERRA levels, telomeric R-loop formation, telomere-induced DNA damage foci formation, particularly during DNA replication stress, and telomere loss. WY2 thereby maintains ALT telomere integrity by modifying TERRA levels and the development of R-loops at telomeres. WY2 also affects the amounts of TERRAs and telomeric R-loops in non-ALT HeLa cells; however, its removal resulted in a trend toward telomere lengthening rather than telomere shortening. The variation in telomere length phenotype between telomerase-positive and ALT cancer cells may be attributable to a number of factors, including disparities in TERRA and R-loop levels in these cancer cells, which will be the focus of our future research. Based on these findings, we propose that WY2 regulates TERRA expression and inhibits TERRAs from creating RNA:DNA hybrids like R-loops at telomeres. WY2 depletion causes TERRA and telomeric R-loop accumulation, which affects telomere length equilibrium in human cancer cells. WY2 represents a novel telomere regulator because of its capacity to maintain telomere integrity in human cancer cells. Understanding WY2's role at telomeres will likely yield novel insights into telomere maintenance pathways and therapeutic avenues.