Vaccine and Gene Therapy Institute, Oregon Health and Science University, Beaverton, Oregon, USA
Vaccine and Gene Therapy Institute, Oregon Health and Science University, Beaverton, Oregon, USA.
mSphere. 2020 Aug 5;5(4):e00582-20. doi: 10.1128/mSphere.00582-20.
Regulation of epidermal growth factor (EGF) receptor (EGFR) signaling is critical for the replication of human cytomegalovirus (HCMV) as well as latency and reactivation in CD34 hematopoietic progenitor cells. HCMV microRNAs (miRNAs) provide a means to modulate the signaling activated by EGF through targeting components of the EGFR signaling pathways. Here, we demonstrate that HCMV miR-US5-2 directly downregulates the critical EGFR adaptor protein GAB1 that mediates activation and sustained signaling through the phosphatidylinositol 3-kinase (PI3K) and MEK/extracellular signal-regulated kinase (ERK) pathways and cellular proliferation in response to EGF. Expression of HCMV UL138 is regulated by the transcription factor early growth response gene 1 (EGR1) downstream of EGFR-induced MEK/ERK signaling. We show that by targeting GAB1 and attenuating MEK/ERK signaling, miR-US5-2 indirectly regulates EGR1 and UL138 expression, which implicates the miRNA in critical regulation of HCMV latency. Human cytomegalovirus (HCMV) causes significant disease in immunocompromised individuals, including transplant patients. HCMV establishes latency in hematopoietic stem cells in the bone marrow. The mechanisms governing latency and reactivation of viral replication are complex and not fully understood. HCMV-encoded miRNAs are small regulatory RNAs that reduce protein expression. In this study, we found that the HCMV miRNA miR-US5-2 targets the epidermal growth factor receptor (EGFR) adaptor protein GAB1 which directly affects downstream cellular signaling pathways activated by EGF. Consequently, miR-US5-2 blocks the EGF-mediated proliferation of human fibroblasts. Early growth response gene 1 (EGR1) is a transcription factor activated by EGFR signaling that regulates expression of HCMV UL138. We show that miR-US5-2 regulates UL138 expression through GAB1-mediated downregulation of the signaling pathways that lead to EGR1 expression. These data suggest that miR-US5-2, through downregulation of GAB1, could play a critical role during reactivation from latency by reducing proliferation and UL138 expression.
表皮生长因子（EGF）受体（EGFR）信号的调节对于人类巨细胞病毒（HCMV）的复制以及 CD34 造血祖细胞中的潜伏和再激活至关重要。HCMV microRNAs（miRNAs）通过靶向 EGFR 信号通路的组成部分，提供了一种调节 EGF 激活的信号的方法。在这里，我们证明 HCMV miR-US5-2 直接下调关键的 EGFR 衔接蛋白 GAB1，该蛋白通过磷脂酰肌醇 3-激酶（PI3K）和 MEK/细胞外信号调节激酶（ERK）途径以及细胞增殖来介导 EGF 激活和持续信号。对 HCMV UL138 的表达受转录因子早期生长反应基因 1（EGR1）的调节，该转录因子是 EGFR 诱导的 MEK/ERK 信号下游的。我们表明，通过靶向 GAB1 和减弱 MEK/ERK 信号，miR-US5-2 间接调节 EGR1 和 UL138 的表达，这表明 miRNA 对 HCMV 潜伏的关键调节。人巨细胞病毒（HCMV）在免疫功能低下的个体中引起重大疾病，包括移植患者。HCMV 在骨髓中的造血干细胞中建立潜伏。病毒复制潜伏和再激活的机制很复杂，尚未完全理解。HCMV 编码的 miRNAs 是小的调节 RNA，可降低蛋白质表达。在这项研究中，我们发现 HCMV miRNA miR-US5-2 靶向表皮生长因子受体（EGFR）衔接蛋白 GAB1，该蛋白直接影响 EGF 激活的下游细胞信号通路。因此，miR-US5-2 阻断了 EGF 介导的人成纤维细胞增殖。早期生长反应基因 1（EGR1）是一种由 EGFR 信号激活的转录因子，可调节 HCMV UL138 的表达。我们表明，miR-US5-2 通过 GAB1 介导的信号通路下调来调节 UL138 的表达，该信号通路导致 EGR1 表达。这些数据表明，miR-US5-2 通过下调 GAB1，通过减少增殖和 UL138 表达，在从潜伏中重新激活过程中可能发挥关键作用。
