Abstract
Human BST-2 (hBST-2) has been identified as a cellular antiviral factor that blocks the release of various enveloped viruses. Orthologues of BST-2 have been identified in several species, including human, monkeys, pig, mouse, cat and sheep. All have been reported to possess antiviral activity. Duplication of the BST-2 gene has been observed in sheep and the paralogues are referred to as ovine BST-2A and BST2-B, although only a single gene corresponding to BST-2 has been identified in most species. In this study, we identified three isoforms of bovine BST-2, named bBST-2A1, bBST-2A2 and bBST-2B, in bovine cells treated with type I interferon, but not in untreated cells. Both bBST-2A1 and bBST-2A2 are posttranslationally modified by N-linked glycosylation and a GPI-anchor as well as hBST-2, while bBST-2B has neither of these modifications. Exogenous expression of bBST-2A1 or bBST-2A2 markedly reduced the production of bovine leukemia virus and vesicular stomatitis virus from cells, while the antiviral activity of bBST-2B was much weaker than those of bBST-2A1 and bBST-2A2. Our data suggest that bBST-2A1 and bBST-2A2 function as part of IFN-induced innate immunity against virus infection. On the other hand, bBST-2B may have a different physiological function from bBST-2A1 and bBST-2A2.
Highlights
Human BST-2 was first identified as a cellular restriction factor that blocks the release of HIV-1 in the absence of the viral accessory protein, Vpu [1,2]
BST-2 consists of four domains, i.e., an N-terminal cytoplasmic tail (CT), a single transmembrane domain, an extracellular domain and a C-terminal glycosylphosphatidyl inositol (GPI) anchor, and both ends of this molecule are associated with the plasma membrane [19]
For molecular cloning of the complete coding regions, we designed primer sets specific for each of these bovine BST-2 genes–bBST-2A and bBST-2B–and carried out RT-PCR using RNA extracted from a bovine cell line, Madin–Darby bovine kidney (MDBK) cells, treated with the type I IFN, IFN-a, for 24 h
Summary
Human BST-2 (hBST-2) ( referred to as Tetherin, CD317 or HM1.24) was first identified as a cellular restriction factor that blocks the release of HIV-1 in the absence of the viral accessory protein, Vpu [1,2]. BST-2 consists of four domains, i.e., an N-terminal cytoplasmic tail (CT), a single transmembrane domain, an extracellular domain and a C-terminal glycosylphosphatidyl inositol (GPI) anchor, and both ends of this molecule are associated with the plasma membrane [19]. Both the N-terminal transmembrane domain and C-terminal GPI anchor are essential for the antiviral activity of hBST-2 against HIV-1 [20]. BST-2 appears to inhibit HIV-1 release by directly tethering virions to cells, briefly by anchoring one end of the molecule on the cell membrane and the other end on the viral envelope
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