Inhibition of TRF2 accelerates telomere attrition and DNA damage in naïve CD4 T cells during HCV infection

Abstract

T cells play a crucial role in viral clearance and vaccine responses; however, the mechanisms that regulate their homeostasis during viral infections remain unclear. In this study, we investigated the machineries of T-cell homeostasis and telomeric DNA damage using a human model of hepatitis C virus (HCV) infection. We found that naïve CD4 T cells in chronically HCV-infected patients (HCV T cells) were significantly reduced due to apoptosis compared with age-matched healthy subjects (HSs). These HCV T cells were not only senescent, as demonstrated by overexpression of aging markers and particularly shortened telomeres; but also DNA damaged, as evidenced by increased dysfunctional telomere-induced foci (TIF). Mechanistically, the telomere shelterin protein, in particular telomeric repeat binding factor 2 (TRF2) that functions to protect telomeres from DNA damage, was significantly inhibited posttranscriptionally via the p53-dependent Siah-1a ubiquitination. Importantly, knockdown of TRF2 in healthy T cells resulted in increases in telomeric DNA damage and T-cell apoptosis, whereas overexpression of TRF2 in HCV T cells alleviated telomeric DNA damage and T-cell apoptosis. To the best of our knowledge, this is the first report revealing that inhibition of TRF2 promotes T-cell telomere attrition and telomeric DNA damage that accelerates T-cell senescent and apoptotic programs, which contribute to naïve T-cell loss during viral infection. Thus, restoring the impaired T-cell telomeric shelterin machinery may offer a new strategy to improve immunotherapy and vaccine response against human viral diseases.

Inhibition of topoisomerase IIA (Top2α) induces telomeric DNA damage and T cell dysfunction during chronic viral infection

“…These results indicate that ICRF-193-induced, Top2α-mediated topological DDR involves dynamic activation and depletion of ATM. These are in line with our recent findings of ATM dynamics in healthy CD4 T cells treated with KML001 or Top1 inhibitor 8,9 and in CD4 T cells derived from patients with chronic HCV and/or HIV infection [5][6][7] .…”

“…TRF1 was also slightly downregulated, but TRF1-interacting nuclear protein 2 (TIN2) was slightly upregulated, while telomere protection protein 1 (TPP1), repressor/activator protein 1 (RAP1), and protection of telomere 1 (POT1) remained unchanged. These findings truly recapitulate the results we observed in CD4 T cells derived from HCV and/or HIV-infected patients 6,7 . Since the primary functions of TRF2 are to protect telomeres from unwanted DNA damage and to recruit telomerase to telomeres, its inhibition may lead to telomere uncapping or deprotection as well as telomerase deprivation from telomeres.…”

“…Human telomeres consist of triple guanine repeats (TTAGGG) that are sensitive to DNA damage 34,35 . We hypothesized that Top2α inhibition-mediated genomic DNA damage may affect telomeres as we have previously shown for telomere erosion in T cells derived from virus-infected subjects [5][6][7][8][9] . To determine telomeric DNA damage in Top2 inhibitor-treated T cells, we measured the number of dysfunctional telomereinduced foci (TIF, a hallmark of telomeric DNA damage 36,37 ) by examining the colocalization of 53BP1/ TRF1 (p53-binding protein 1/telomeric repeat-binding factor 1) using confocal microscopy.…”

“…4g), which are consistent with the data above showing Top2α inhibition, Top2cc accumulation, PARP1 induction, and apoptosis in these cells ( Figs. 1-4) [5][6][7][8][9] .…”

“…T cells play a critical role in control of viral infection. In studying the role of T cell dysregulation in viral persistence in humans, we and others have previously shown that chronic viral infections can cause premature T cell aging and immune senescence, as evidenced by the expression of aging markers and particularly, accumulation of DNA damage [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] . However, the underlying mechanisms remain unclear.…”