HUMAN THIOREDOXIN ADULT T-CELL LEUKEMIA-DERIVED FACTOR ACTIVATES THE ENHANCER BINDING-PROTEIN OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 BY THIOL REDOX CONTROL MECHANISM

Transcription from the human immunodeficiency virus type 1 (HIV-1) provirus is activated by a cellular factor, NF-chi-B, recognizing the tandemly repeated 10-base-pair sequences, termed the chi-B sequence, present in the enhancer region within the viral long terminal repeat (LTR). Using electrophoretic mobility shift assay (EMSA), which demonstrates specific DNA - protein interaction in vitro, we could demonstrate that reducto-oxidative modulation of NF-chi-B dramatically changes its DNA binding activity and that a cellular physiological reducing catalyst, thioredoxin (TRX) also known as adult T cell leukemia derived factor (ADF), fully restored the DNA-binding activity of the oxidized NF-chi-B. We also observed that purified TRX/ADF protein could augment gene expression from HIV LTR as demonstrated by transient chloramphenicol acetyltransferase (CAT) assay. These observations confirmed the previous notion that ADF might be an inducing factor of cellular interleukin-2 receptor alpha-subunit (IL-2R-alpha) through the chi-B sequence that is a common central cis-regulatory element in both IL-2R-alpha and HIV gene expression. These observations indicate that reducto-oxidative regulation (or redox regulation) of a cysteine residue(s) on the NF-chi-B molecule might play an important role in its specific DNA interaction and that it might provide a clue to the understanding of a pathway of cellular signal transduction to NF-chi-B that is independent from the known pathways involving protein phosphorylation.