The site of HIV-1 integration in the human genome determines basal transcriptional activity and response to Tat transactivation

Abstract

Because of the heterogeneity of chromatin, the site of integration of human immunode®ciency virus (HIV) in the genome could have dramatic effects on its transcriptional activity. We have used an HIV-1-derived retroviral vector, in which the green¯uorescent protein is under the control of the HIV promoter, to generate by infection 34 Jurkat clonal cell lines each containing a single integration of the HIV-1 vector. In the absence of Tat, a 75-fold difference in expression level between the highest and lowest expressing clones was observed. Basal promoter activity was low in 80% of the clones and moderate to high in the remaining 20% of clones. We found that differences in expression levels are due to the integration site and are not controlled by DNA methylation or histone acetylation. Tat activated transcription in each clone, and an inverse correlation was observed between basal transcriptional activity and inducibility by Tat. These observations demonstrate that the chromatin environment in¯uences basal HIV gene expression and that the HIV Tat protein activates transcription independently of the chromatin environment.

Transcriptional burst frequency and burst size are equally modulated across the human genome

“…2A). To focus on measuring the intrinsic fluctuation dynamics of the genomic region surrounding the vectorintegration site, we utilized a vector encoding the HIV-1 LTR promoter, which is relatively weak and heavily influenced by the expression dynamics of the local chromatin environment (22).…”

Prostratin Antagonizes HIV Latency by Activating NF-κB

“…These findings suggest that repeated rounds of stimulation may be required to purge the entire pool of latently infected cells. Differences in the chromatin environment immediately surrounding the HIV integration locus may play an important role in controlling this functional response as well as the basal and induced levels of transcription (43).…”

Evaluation of Tet-on system to avoid transgene down-regulation in ex vivo gene transfer to the CNS

“…This apparent lack of preferential integration of an LV vector in cultured cells is supported by a recent report. 37 This raises the possibility that elements in the LV vector serve to protect the transcriptional unit from position effects through an as yet undescribed insulating activity in the virus vector similar to cHS4. The observed long-term in vivo expression of LV vectors 10 might therefore partly be mediated through an insulating effect of the vector that serves to prohibit access of negative factors.…”