Regulation of viral p6 and cytokine promoter by Parvovirus B19 nonstructural protein 11 kD

Abstract:

[Background] Human Parvovirus B19 (B19 virus) is a member of the two Parvoviriade families that cause human diseases. The unique viral p6 promoter in B19 virus controls all the viral mRNA transcription. Previous research shows that some transcription factor binding sites (TFBSs) within p6 and nonstructural protein NS1 of B19 virus are both involved in regulation of p6 activity. However, effects of other TFBSs or viral proteins on p6 activtiy have not been reported. [Objective] Here, we investigate the roles of 11 kD protein in regulation of the activities of B19 p6 promoter as well as some cytokine promoters. [Methods] Based on bioinformatics methods, we predicted some new TFBSs and identified the CpG island in p6 region. In vitro methylation assay was carried out to study the effect of CpG on p6 activity. Meanwhile, EGFP and luciferase reporter system were employed to detect the activities of p6 and other cytokine promoters. [Results] Consistent with previous research, p6 shows similar high activity in different non-permissive cells. The truncated p6 mutation assay indicated that CTCF, YY1, STAT3, Sp1/3 and E2F7 binding sites at nt. 302?479 played significant roles in maintaining p6 promoter activity. In addition, in vitro methylation assay demonstrated that CpG methylation on p6 inhibited its promoter activity. Interestingly, though 11 kD protein did not regulate p6 activity, it increased the promoter activity of TNF-α, IL6, STAT3 significantly. [Conclusion] Our findings imply that the newly discovered TFBSs and CpG island in p6 are essential for the maintenance of p6 promoter activity. Meanwhile, the association between nonstructural protein 11 kD and cytokine promoter suggests that 11 kD may participate in B19 virus host interaction by regulating the cytokine factor expression.