Comparison of hAPOBEC3 isoforms expressed in different cell lines indicated that hA3B was the most likely candidate for a restrictive hA3. MXMRV (MX) viruses containing hA3B, 293T cells were transiently transfected with pVP62 or pMXMRV along with HA-hA3B or pcDNA3 (control). Gag MB-7133 and hA3B proteins in the cell lysates and the virions released from the transfected 293T cells were detected by SDS-PAGE and Western blotting for anti-p30CA and anti-HA antibodies. hA3B was incorporated into XMRV and MXMRV virions with equivalent efficiency. 1742-4690-9-58-S3.pdf (1.1M) GUID:?74F57F62-2D20-450F-8D28-CF866FF6340D Additional file 4 Figure S4. Inhibition of HIV infection by hA3B. 293T cells were transiently co-transfected with the expression vectors, pCMV-dR8.74 (HIV-1 Gag-Pol), pMD2.G (VSV-G), pLVTHM (HIV-1-based vector expressing EGFP, http://www.addgene.org/12247) along with HA-hA3B or pcDNA3 (control). A) HIV-1 Gag proteins and hA3B in the transfected 293T cells and viruses were detected by SDS-PAGE and Western blot with anti-p24 and anti-HA antibodies. The pseudoviruses with hA3B released from the transfected 293T cells were used for titering HIV-1 infectivity. B) The vector stocks produced in the panel A MB-7133 were used to infect fresh 293T cells, and the GFP-positive cells were counted 2?days post-infection. The relative numbers of GFP-positive cells, normalized for p24 in the vector stocks, are shown. The value for the control vector lacking hA3B (pcDNA3) was set at 1. C) As a second measure of infectivity, equal volumes of vector stocks shown in the panel A were used for infection of fresh 293T cells. At 3?days post-infection, the amount of EGFP protein in the infected cells was determined by SDS-PAGE and Western blotting with anti-EGFP antibodies. The Western blot data and the relative volumes of each sample loaded on the gel are shown. When corrected for the amount of vector (as assessed by p24 protein), the inhibition of HIV vector infection by HA-hA3B was consistent with the infectivity assay in the panel B. 1742-4690-9-58-S4.pdf (1.0M) GUID:?F5407375-240E-4F3B-9B5F-77324BB9CC75 Additional file 5 Table S1. Endogenous ecotropic, xenotropic, polytropic and modified polytropic MuLVs Rabbit Polyclonal to CLTR2 in the sequenced C57BL genome. GenBank accession numbers are provided for the BAC clones containing the ERVs along with the positions of the viral sequences and the presence or absence of the consensus glyco-gag sequence is noted. 1742-4690-9-58-S5.xls (38K) GUID:?E3FBB425-DD35-48DA-BBC6-C408AE39571A Abstract Background One of the unique features of gammaretroviruses is that they contain an additional extended form of Gag, glyco-gag, which initiates in the leader sequence. MuLV glyco-gag, gPr80Gag, promotes retrovirus replication and disease progression. Although virtually all infectious MuLVs encode glyco-gag, XMRV (xenotropic murine leukemia virus-related virus) lacks the classical gPr80Gag sequence. We examined XMRV to determine if its leader sequence contains glyco-gag activity, whether the presence of conventional gPr80Gag affects replication of XMRV, and we describe the evolution of glyco-gag-deficient MuLVs in Mus. Results We introduced several mutations disrupting two putative but noncanonical glyco-gag proteins in the leader sequence region in XMRV and found that those mutations did not affect virus release nor susceptibility to the antiviral activity of hA3G (human APOBEC3G). A chimeric XMRV encoding the Moloney MuLV (M-MuLV) leader sequence (MXMRV) demonstrated that M-MuLV glyco-gag facilitated MXMRV release and increased infectivity. Infectivity assays with several cell lines showed that glyco-gag increases XMRV infectivity in all cell lines tested, but the level of this increase varies in different cell lines. Because MuLV glyco-gag counteracts mouse APOBEC3, we investigated whether M-MuLV glyco-gag enhances XMRV infection by counteracting human APOBEC3. Comparison of hAPOBEC3 isoforms expressed in different cell lines indicated that hA3B was the most likely candidate for a restrictive hA3. However over-expression of hA3B showed no enhanced restriction of infection by XMRV MB-7133 compared to MXMRV. Endogenous MuLVs in the sequenced mouse genome were screened for canonical glyco-gag, which was identified in two clades of xenotropic MuLVs (X-MuLVs) and ecotropic MuLVs, but not in other X-MuLVs or in any polytropic MuLVs. Conclusions M-MuLV glyco-gag facilitates XMRV replication, and the leader sequence region in XMRV does not encode proteins equivalent to M-MuLV glyco-gag. The fact that the ability of glyco-gag to enhance XMRV infection MB-7133 varies in different cell lines suggests a glyco-gag sensitive restrictive factor that further reduces XMRV infectivity. The M-MuLV glyco-gag enhancement for XMRV replication is through a hAPOBEC3 independent mechanism. The absence of glyco-gag in MuLVs carried by western European mice suggests that loss of this sequence is MB-7133 a relatively recent.