G-quadruplex-interacting compounds alter latent DNA replication and episomal persistence of KSHV

Abstract

Kaposi’s sarcoma associated herpesvirus (KSHV) establishes life-long latent infection by persisting as an extra-chromosomal episome in the infected cells and by maintaining its genome in dividing cells. KSHV achieves this by tethering its epigenome to the host chromosome by latency associated nu- clear antigen (LANA), which binds in the terminal repeat (TR) region of the viral genome. Sequence analysis of the TR, a GC-rich DNA element, identified several potential Quadruplex G-Rich Sequences (QGRS). Since quadruplexes have the tendency to obstruct DNA replication, we used G-quadruplex sta- bilizing compounds to examine their effect on la- tent DNA replication and the persistence of viral epi- somes. Our results showed that these G-quadruplex stabilizing compounds led to the activation of dor- mant origins of DNA replication, with preferential bi- directional pausing of replications forks moving out of the TR region, implicating the role of the G-rich TR in the perturbation of episomal DNA replication. Over time, treatment with PhenDC3 showed a loss of viral episomes in the infected cells. Overall, these data show that G-quadruplex stabilizing compounds retard the progression of replication forks leading to a reduction in DNA replication and episomal main- tenance. These results suggest a potential role for G-quadruplex stabilizers in the treatment of KSHV- associated diseases.