The N Terminus of Adenovirus Type 12 E1A Inhibits Major Histocompatibility Complex Class I Expression by Preventing Phosphorylation of NF-κB p65 Ser276 through Direct Binding
The N Terminus of Adenovirus Type 12 E1A Inhibits Major Histocompatibility Complex Class I Expression by Preventing Phosphorylation of NF-κB p65 Ser276 through Direct Binding
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DOI：
10.1128/jvi.02317-09
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发表时间：
2010-08-01
影响因子：
5.4
通讯作者：
Ricciardi, Robert P.
中科院分区：
文献类型：
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作者：
Jiao, Junfang;Guan, Hancheng;Ricciardi, Robert P.
人12型致癌腺病毒（Ad 12）采用的免疫逃逸策略涉及通过使反式激活因子NF-κ B（p50/p65）失活来下调I类主要组织相容性复合物（MHC-I）转录。这是由Ad 12 E1 A蛋白（E1 A-12）完成的，它阻止NF-κ B被蛋白激酶A催化亚基（PKAc）磷酸化。在这项研究中，我们研究了E1 A-12和NF-κ B B之间的相互作用。我们的数据显示，保留N-末端66个氨基酸的E1 A-12突变体在结合p65、防止p65-Ser（276）磷酸化和抑制反式激活方面与野生型E1 A-12蛋白（266个氨基酸）一样有效。相反，非致瘤性腺病毒5型E1 A蛋白（E1 A-5）和其他E1 A-12突变体缺乏的N-末端区域的这些活动严重缺陷。进一步的研究表明，由E1 A-12残基1 - 40组成的N-末端肽能够在体外直接与p65结合，并阻止PKAc磷酸化p65-Ser（276）。在N末端缺失的情况下，E1 A-12与p65的结合几乎完全丧失。这些发现为E1 A-12 N末端作为NF-κ B结合结构域的作用提供了坚实的证据。值得注意的是，这项研究表明，E1 A-12 N末端阻止PKAc进入p65，以解释Ser（276）磷酸化不足。E1 A-12 N末端与p65的相互作用是Ad 12如何下调MHC-I转录并通过逃避细胞毒性T淋巴细胞而促进肿瘤发生的关键解释。
The immune-escape strategy employed by human oncogenic adenovirus type 12 (Ad12) involves downregulation of major histocompatibility complex class I (MHC-I) transcription by disabling the transactivator NF-kappa B (p50/p65). This is accomplished by the Ad12 E1A protein (E1A-12), which prevents NF-kappa B from becoming phosphorylated by the protein kinase A catalytic subunit (PKAc). In this study, we examined the interactions between E1A-12 and NF-kappa B. Our data show that an E1A-12 mutant retaining the N-terminal 66 amino acids was as effective as the wild-type E1A-12 protein (266 amino acids) in binding p65, preventing phosphorylation of p65-Ser(276), and inhibiting transactivation. In contrast, the nontumorigenic adenovirus type 5 E1A protein (E1A-5) and other E1A-12 mutants lacking the N-terminal regions were severely defective in these activities. Further studies revealed that an N-terminal peptide consisting of residues 1 to 40 of E1A-12 was able to associate directly with p65 in vitro and prevent PKAc from phosphorylating p65-Ser(276). In the absence of the N terminus, there is an almost complete loss of E1A-12 binding to p65. These findings provide solid evidence for the role of the E1A-12 N terminus as an NF-kappa B binding domain. Significantly, this study indicates that the E1A-12 N terminus prevents PKAc from gaining access to p65 to account for Ser(276) hypophosphorylation. The E1A-12 N terminus interaction with p65 serves as a key explanation of how Ad12 downregulates MHC-I transcription and contributes to oncogenesis by escaping cytotoxic T lymphocytes.