Zscan4 Contributes to Telomere Maintenance in Telomerase-Deficient Late Generation Mouse ESCs and Human ALT Cancer Cells
Jiameng Dan,
Zhongcheng Zhou,
Fang Wang,
Hua Wang,
Renpeng Guo,
David L. Keefe,
Lin Liu
Affiliations
Jiameng Dan
State Key Laboratory of Medicinal Chemical Biology, Department of Cell Biology and Genetics, College of Life Sciences, Nankai University, Tianjin 300071, China
Zhongcheng Zhou
State Key Laboratory of Medicinal Chemical Biology, Department of Cell Biology and Genetics, College of Life Sciences, Nankai University, Tianjin 300071, China
Fang Wang
Department of Obstetrics and Gynecology, New York University Langone Medical Center, New York, NY 10016, USA
Hua Wang
State Key Laboratory of Medicinal Chemical Biology, Department of Cell Biology and Genetics, College of Life Sciences, Nankai University, Tianjin 300071, China
Renpeng Guo
State Key Laboratory of Medicinal Chemical Biology, Department of Cell Biology and Genetics, College of Life Sciences, Nankai University, Tianjin 300071, China
David L. Keefe
Department of Obstetrics and Gynecology, New York University Langone Medical Center, New York, NY 10016, USA
Lin Liu
State Key Laboratory of Medicinal Chemical Biology, Department of Cell Biology and Genetics, College of Life Sciences, Nankai University, Tianjin 300071, China
Proper telomere length is essential for indefinite self-renewal of embryonic stem (ES) cells and cancer cells. Telomerase-deficient late generation mouse ES cells and human ALT cancer cells are able to propagate for numerous passages, suggesting telomerase-independent mechanisms responding for telomere maintenance. However, the underlying mechanisms ensuring the telomere length maintenance are unclear. Here, using late generation telomerase KO (G4 Terc-/-) ESCs as a model, we show that Zscan4, highly upregulated in G4 Terc-/- ESCs, is responsible for the prolonged culture of these cells with stably short telomeres. Mechanistically, G4 Terc-/- ESCs showed reduced levels of DNA methylation and H3K9me3 at Zscan4 promoter and subtelomeres, which relieved the expression of Zscan4. Similarly, human ZSCAN4 was also derepressed by reduced H3K9me3 at its promoter in ALT U2 OS cells, and depletion of ZSCAN4 significantly shortened telomeres. Our results define a similar conserved pathway contributing to the telomere maintenance in telomerase-deficient late generation mESCs and human ALT U2OS cancer cells.
