110 - Mechanisms of HIV-1 Tat-Mediated Regulation of the Manganese-Superoxide Dismutase Promoter

Abstract

The introduction of antiretroviral therapies is largely responsible for the development of chronic HIV infection, but long-term exposure to viral proteins can contribute to pulmonary and cardiac complications such as HIV-Associated pulmonary arterial hypertension (HA-PAH). Oxidative stress and inflammation are two major drivers of pulmonary pathology in idiopathic pulmonary arterial hypertension (iPAH) and could also be involved in the pathogenesis of HA-PAH. We have reported previously that the HIV transcriptional regulator, Tat (trans-activator of transcription), can induce oxidative responses by depleting cellular glutathione and contributing to the inhibition of mitochondrial manganese-superoxide dismutase (MnSOD, sod2). We also previously defined Tat-regulated elements within the proximal regions of the human sod2 promoter, designated Tat-sensitive Sp-responsive elements (TSS). We’ve seen that Tat alters the pattern of binding by the Sp1 and Sp3 transcription factors on the sod2 TSS, causing transcriptional repression. Recently we observed evidence of Sp-binding sites containing Tat-regulated regions within more distal sections of the sod2 promoter which we have termed the DTSS (Distal Tat-sensitive Sp elements). The previous discoveries that Tat regulates the proximal promoter by changing the patterns of Sp binding prompted us to investigate the mechanisms of Tat regulation on the distal regions of the promoter. In this study, we transiently transfected pGL3B luciferase-reporter plasmids containing varying regions of the sod2 promoter in the presence or absence of Tat to determine if Tat influences the transcription of this promoter through distal elements. Our data suggests that Tat-mediated regulation of the sod2 promoter is different in Human Pulmonary Artery Endothelial cells (HPAEC) than in HeLa cells. We also present evidence that the different isoforms of Tat, full-length Tat101 and Tat86, regulate the sod2 promoter differently. We therefore hypothesize that the interactions of Tat with Sp, and possibly other, transcription factors are contributing to the observed differences in sod2 regulation in the different cells types.