The effects of multiple UV exposures on HIV-LTR expression

Area of Science:

• Molecular Biology
• Virology
• Cellular Stress Response

Background:

• Cellular stress, including UV radiation, is known to induce transcription from the human immunodeficiency virus (HIV) long terminal repeat (LTR).
• Understanding the impact of repeated stress on HIV transcription is crucial for managing viral latency and reactivation.

Purpose of the Study:

• To investigate the effects of multiple UVC exposures on HIV-LTR-driven gene expression.
• To determine dose-dependent and cumulative effects of UVC on HIV transcription.

Main Methods:

• Utilized HeLa cells stably transfected with an HIV-LTR sequence driving a chloramphenicol acetyl transferase (CAT) reporter gene.
• Administered single and sequential UVC (254 nm) exposures at varying doses (5-37.5 J m-2).
• Assayed CAT expression in cell lysates at different time points post-exposure (24-72 h).

Main Results:

• Low UVC doses (< or = 5 J m-2) had no significant effect on CAT expression.
• A single 10 J m-2 UVC dose induced up to 29-fold CAT expression.
• Two sequential 12.5 J m-2 UVC exposures, 24 hours apart, showed an additive effect, equivalent to a single 25 J m-2 dose.
• Maximal induction of HIV-LTR-CAT expression was observed with single doses ranging from 25 to 37.5 J m-2.
• Multiple exposures at low or high doses did not yield an additive effect.

Conclusions:

• Sequential, moderate UVC exposures can lead to additive induction of HIV-LTR transcription.
• The response to UVC is dose-dependent, with maximal induction occurring at specific higher doses.
• Understanding these dynamics is important for predicting HIV reactivation under conditions of repeated cellular stress.