HTLV-1 Tax upregulates early growth response protein 1 through nuclear factor-?B signaling.

ABSTRACT: Human T cell leukemia virus type 1 (HTLV-1) is a complex retrovirus that causes adult T cell leukemia (ATL) in susceptible individuals. The HTLV-1-encoded oncoprotein Tax induces persistent activation of the nuclear factor-?B (NF-?B) pathway. Early growth response protein 1 (EGR1) is overexpressed in HTLV-1-infected T cell lines and ATL cells. Here, we showed that both Tax expression and HTLV-1 infection promoted EGR1 overexpression. Loss of the NF-?B binding site in the EGR1 promotor or inhibition of NF-?B activation reduced Tax-induced EGR1 upregulation. Tax mutants unable to activate NF-?B induced only slight EGR1 upregulation as compared with wild-type Tax, confirming NF-?B pathway involvement in EGR1 regulation. Tax also directly interacted with the EGR1 protein and increased endogenous EGR1 stability. Elevated EGR1 in turn promoted p65 nuclear translocation and increased NF-?B activation. These results demonstrate a positive feedback loop between EGR1 expression and NF-?B activation in HTLV-1-infected and Tax-expressing cells. Both NF-?B activation and Tax-induced EGR1 stability upregulated EGR1, which in turn enhanced constitutive NF-?B activation and facilitated ATL progression in HTLV-1-infected cells. These findings suggest EGR1 may be an effective anti-ATL therapeutic target.

SUBMITTER: Huang Q 

PROVIDER: S-EPMC5584236 | biostudies-literature | 2017 Aug

REPOSITORIES: biostudies-literature