The immediate-early 1 (IE1) and IE2 proteins encoded by the major immediate-early (MIE) transcription unit of cytomegaloviruses are thought to play key roles in the switch between latent- and lytic-cycle infection. Whilst IE2 is essential for triggering the lytic cycle, the exact roles of IE1 have not been resolved. An MIE–exon 4-deleted rat cytomegalovirus (ΔIE1) failed to synthesize the IE1 protein and did not disperse promyelocytic leukaemia bodies early post-infection, but was still capable of normal replication in fibroblast cell culture. However, ΔIE1 had a diminished ability to infect salivary glands persistently and to reactivate from spleen explant cultures . Quantification of viral genomes in spleens of infected animals revealed a reduced amount of ΔIE1 virus produced during acute infection, suggesting a role for IE1 as a regulator in establishing a chronic or persistent infection, rather than in influencing the latency or reactivation processes more directly.


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vol. , part 3, pp. 616–621

Southern blot analysis to measure the equivalency of p.f.u. : particle ratios

PCR analysis to verify the integrity of exons 3 and 5 in ΔIE1ex4

PCR analysis to detect viral DNA in animals infected with ΔIE1ex4

Representative Western blot of virus isolated from salivary gland or reactivated from spleen from persistently (120 days) infected animals

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