Human Cytomegalovirus PUL97 Upregulates SOCS3 Expression Via Transcription Factor RFX7 In Neural Progenitor Cells

Congenital Human cytomegalovirus(HCMV)infection can cause severe damage to the developing fetal central nervous system(CNS).Currently,effective prevention and treatment methods are missing,and the teratogenic mechanism of HCMV is not well understood.In congenital HCMV infection,the ventricular zone(VZ)and subventricular zone(SVZ)are particularly sensitive to HCMV,as neural progenitor cells(NPCs)are the main cell types in these area and the primary targets of HCMV.NPCs differentiate into neurons firstly,and then differentiate into glial cells during neural differentiation.These neural cells migrate during differentiation to form cerebral cortex structures,and form functional connections with each other to fulfil neurological functions.This process is precisely regulated by various cell-signaling pathways(Notch pathway),which ensure the orderly brain development.The JAK-STAT3 pathway is essential for regulating NPCs differentiation and self-renewal.In the early study,we found that HCMV infection could lead to down-regulate markers of NPCs and NPC abnormal differentiation.Based on the congenital HCMV infection human cell model established by our lab,we show that HCMV causes the significant increase of Suppressors of cytokine signaling 3(SOCS3),which is a multipathway-related regulatory factor affecting NPCs maintenance and differentiation and the inhibitor of JAK-STAT3 pathway.The screening for viral proteins responsible for dysregulating SOCS3 expression revealed that p UL97 protein activates SOCS3 transcription and upregulates SOCS3 expression through kinase activity.Mass spectrometry analysis of host proteins interacting with p UL97 identified that a transcription factor,Regulatory factor X 7(RFX7),was involved in the regulation of SOCS3 expression,and p UL97 can activate RFX7 via phosphorylation to allow the binding of RFX7 to SOCS3 promoter,which in turn enhanced SOCS3 transcription.In addition,knocking down p UL97 or RFX7 individually inhibited SOCS3 upregulation in NPCs during HCMV infection.Moreover,we demonstrated that overexpression of SOCS3 in NPCs inhibited their proliferation,migration and neuralsphere formation capacity,and overexpression of SOCS3 in vivo disturbed cortical brain development.In addition,in the congenital CMV infection mouse model,CMV infection can observably induce SOCS3 expression in fetal brain,which suggested that SOCS3 plays an important role in congenital CMV neuropathy.The study showed that HCMV p UL97 up-regulated SOCS3 expression by activating RFX7,and revealed the negative effects of highly sustained SOCS3 expression on neurogenesis.These findings help to elucidate the developmental neuropathogenesis caused by congenital CMV infection.