FOXO Transcription Factors Activate Alternative Major Immediate Early Promoters to Induce Human Cytomegalovirus Reactivation

Abstract

32A key step during viral reactivation from latency is the re-expression of viral genes. 33Hematopoietic progenitor cells (HPCs) support human cytomegalovirus (HCMV) 34 latency, and their differentiation triggers cellular cues that drive reactivation. A key step 35 during HCMV reactivation in latently infected HPCs is re-expression of viral genes. We 36 recently determined that the major immediate early promoter (MIEP), which is primarily 37 responsible for MIE gene expression during lytic replication, remains silent during 38 reactivation. Instead, alternative promoters in the MIE locus are induced by reactivation 39 stimuli. Here, we find that forkhead family (FOXO) transcription factors are critical for 40 activation of alternative MIE promoters during HCMV reactivation, as mutating FOXO 41 binding sites in alternative MIE promoters decreased HCMV IE gene expression upon 42 reactivation and significantly decreased the production of infectious virus from latently 43 infected primary CD34 + HPCs. These findings establish a mechanistic link by which 44 infected cells sense environmental cues to regulate latency and reactivation, and 45 emphasize the role of contextual activation of alternative MIE promoters as the primary 46 drivers of reactivation. 47 48 Significance 49 50 Human cytomegalovirus infection is lifelong and persistent. Periodic reactivation of 51 cytomegalovirus poses serious disease risk for immune-compromised patients. A critical 52 driver of reactivation is expression of viral genes from the major immediate early locus. 53Recent paradigm-shifting evidence shows that reactivation is driven from promoters 54 distinct from those that drive replication in permissive cells. Understanding the 55 contextual control of these promoters and how they specifically respond to cellular cues 56 that drive reactivation is critical for establishing future therapies that prevent 57 reactivation. Our findings mechanistically define a previously enigmatic relationship 58 between differentiation and reactivation, and provide potential targets for therapeutic 59 intervention to prevent HCMV reactivation and disease. 60 61 virology 89(Pt 2):359-368.

Hematopoietic stem cells and betaherpesvirus latency

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