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Viruses. 2018 Nov 21;10(11). pii: E656. doi: 10.3390/v10110656.

Viral Proteins U41 and U70 of Human Herpesvirus 6A Are Dispensable for Telomere Integration.

Author information

1
Institut für Virologie, Freie Universität Berlin, Robert von Ostertag-Straße 7-13, 14163 Berlin, Germany. d.wight@fu-berlin.de.
2
Institute for Molecular Infection Biology, Julius-Maximilians-Universität Wϋrzburg, Josef-Schneider-Straße 2, 97080 Wϋrzburg, Germany. nina.wallaschek@uni-wuerzburg.de.
3
Institut für Virologie, Freie Universität Berlin, Robert von Ostertag-Straße 7-13, 14163 Berlin, Germany. aanirbansanyal@gmail.com.
4
Molecular Biology and Biophysics, UConn Health, 263 Farmington Avenue, Farmington, CT 06030-3205, USA. weller@uchc.edu.
5
Department of Microbiology and Immunology, CHU de Québec, Université Laval, Quebec, QC G1V 4G2, Canada. louis.flamand@crchudequebec.ulaval.ca.
6
Institut für Virologie, Freie Universität Berlin, Robert von Ostertag-Straße 7-13, 14163 Berlin, Germany. Benedikt.Kaufer@fu-berlin.de.

Abstract

Human herpesvirus-6A and -6B (HHV-6A and -6B) are two closely related betaherpesviruses that infect humans. Upon primary infection they establish a life-long infection termed latency, where the virus genome is integrated into the telomeres of latently infected cells. Intriguingly, HHV-6A/B can integrate into germ cells, leading to individuals with inherited chromosomally-integrated HHV-6 (iciHHV-6), who have the HHV-6 genome in every cell. It is known that telomeric repeats flanking the virus genome are essential for integration; however, the protein factors mediating integration remain enigmatic. We have previously shown that the putative viral integrase U94 is not essential for telomere integration; thus, we set out to assess the contribution of potential viral recombination proteins U41 and U70 towards integration. We could show that U70 enhances dsDNA break repair via a homology-directed mechanism using a reporter cell line. We then engineered cells to produce shRNAs targeting both U41 and U70 to inhibit their expression during infection. Using these cells in our HHV-6A in vitro integration assay, we could show that U41/U70 were dispensable for telomere integration. Furthermore, additional inhibition of the cellular recombinase Rad51 suggested that it was also not essential, indicating that other cellular and/or viral factors must mediate telomere integration.

KEYWORDS:

HHV-6A; human herpesvirus 6A; latency; recombination; telomere integration

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