RNA Viruses: RNA Roles in Pathogenesis, Coreplication and Viral Load

Poltronieri, Palmiro; Sun, Binlian; Mallardo, Massimo

Incubation of mouse zygotes with 5 -bromodeoxyuridine (BrdU) yields massive incorporation of this nucleoside analogue in newly synthesized DNA; surprisingly, a significant incorporation still occurs in both zygotic pronuclei in the presence of aphidicolin, a specific inhibitor of DNA replication. This aphidicolin-resistant BrdU incorporation is quantitatively abolished when embryos are simultaneously exposed to abacavir, a nucleoside RT inhibitor, thus revealing its RTdependent nature. Moreover, quantitative PCR analysis showed that LINE-1 copies are newly synthesized at the zygote-and two-cell embryo stages and nearly doubled compared to gamete copy number. These findings support the conclusion that RT-dependent amplification of LINE-1 retro-transposons is a distinctive feature of early embryonic genomes [7] .