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Figure 4 | Cell Division

Figure 4

From: Regulation of the retinoblastoma proteins by the human herpesviruses

Figure 4

Expression of nucleotide biosynthetic enzymes during the lytic and latent phases of different classes of human herpesviruses. See text for details. α. During lytic infection HSV-1 does not induce the expression of cellular NBEs (nucleotide biosynthetic enzymes), and thus appears to rely on viral NBEs. It is unclear if the shutoff of host protein synthesis contributes to the absence of host NBE expression. During latency, viral genomes are not replicated and thus no NBEs appear to be required. Reactivation is assumed to be similar to lytic infection with a reliance on viral NBEs. β. During lytic infection HMCV robustly activates the expression of cellular NBEs, likely because it does not encode a full complement of viral NBEs. Reliance on NBEs during latency is not known because it is unclear if the viral genome replicates. However if viral genomic replication occurs, it is likely that cellular NBEs provide the needed nucleotides. Reactivation is assumed to be similar to lytic infection with a reliance on cellular NBEs. γ. During lytic infection EBV inactivates Rb and expresses its own NBEs, so both cellular and viral NBEs might be utilized. Note the shutoff of host protein synthesis during KSHV infection would appear to imply that viral NBEs play a more prominant role in KSHV lytic infection. During latency, viral proteins inactivate Rb and viral NBEs aren't expressed, implying a reliance on viral NBEs. Reactivation is assumed to be similar to lytic infection with a reliance on viral NBEs (for KSHV) or both viral and cellular NBEs (for EBV).

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