Research Paper Volume 3, Issue 4 pp 395—406
Depletion of Ku70/80 reduces the levels of extrachromosomal telomeric circles and inhibits proliferation of ALT cells
- 1 Department of Molecular Microbiology and Immunology, Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
- 2 Department of Biochemistry and Molecular Biology, Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, Los Angeles, CA 90033, USA
Received: March 30, 2011 Accepted: April 14, 2011 Published: April 15, 2011https://doi.org/10.18632/aging.100308
How to Cite
In normal cells, telomeres shorten each time a cell divides ultimately resulting in cell senescence. t In contrast, cancer cells counteract the loss of telomeric DNA either by inducing the expression of telomerase or by activating the Alternative Lengthening of Telomeres (ALT) pathway. ALT cells are characterized by heterogeneous telomeres and the presence of extrachromosomal circular double-stranded DNA molecules containing telomeric repeat sequences. These telomeric circles (t-circles) are thought to be generated through a recombination process and utilized as templates for telomere elongation by rolling-circle-replication, although their precise mechanism of formation and role in telomere maintenance and cell proliferation is largely unknown. Here we show that shRNA-mediated knockdown of the Ku70/80 heterodimer, a factor with functions at both pathological and natural DNA ends, inhibits ALT cell growth and results in a significant decrease in the levels of t-circles without affecting overall telomere length. These findings demonstrate that non homology-based processes contribute to the maintenance of t-circles and proliferation of ALT cells.