Early growth response gene-1 regulates host cell autophagy in HTLV-1 infection

Abstract

Objective To investigate the influence of early growth response gene-1 (EGR1) on the autophagy of host cells following infection with human T cell leukemia virus type 1 (HTLV-1). Methods A HTLV-1-positive cell line MT2 was co-cultured with HeLa cells for 24 h to construct the virus early infection model. Immunoblotting assay was used to detect the expression of HTLV-1 core protein p19 and EGR1. Luciferase reporter gene analysis was used to detect the transcriptional activity of 5′-regulatory sequence of EGR1 at different time points after co-culturing. An effective small interfering RNA (siRNA) targeting EGR1 was screened out and transfected into HeLa cells by Lipofectamine 2000. Then the transfected HeLa cells were co-cultured with the HTLV-1-positive cell line MT2 for 24 h. Immunoblotting assay was used to detect HTLV-1 core protein p19, EGR1 and autophagy-related protein LC3. Real-time PCR was performed to detect viral load. Autophagosome was analyzed by immunofluorescence after co-culturing. Results The expression of EGR1 and the transcriptional activity of pEGR1-luc gradually increased after co-culturing HeLa cells with MT2 cells for 8 h (P<0.01). The expression of EGR1 was positively correlated with host cell autophagy following HTLV-1 infection. The effective siRNA for silencing the expression of EGR1 was obtained and named as siE2. The viral load, the expression of HTLV-1 core protein p19 and the proportion of LC3B/LC3A in the co-culture model were markedly down-regulated by RNA interference with siE2, which was concomitant with a persistent decrease of intracellular autophagosome (P<0.01). Conclusion EGR1 is associated with host cell autophagy and viral replication in HTLV-1 infection. Key words: Early growth response gene-1; Human T-cell leukemia virus type 1; Autophagy; Virus replication