For luminograms, chemiluminescent peroxidase substrate Supersignal? (Pierce) was used. HIV-1-centered vector HIV-Luc and EED protein indicated by DNA transfection of 293T cells. Results During the early phase of HIV-1 illness, a slight negative effect on disease infectivity occurred in EED-expressing cells, which appeared to be dependent on EED-MA connection. At late times post illness, EED Goserelin caused an important reduction of disease production, from 20- to 25-collapse as determined by CAp24 immunoassay, to 10- to 80-collapse based on genomic RNA levels, and MEN2B this decrease was not due to a reduction of Gag protein synthesis. Coexpression of WTNef, or the non-N-myristoylated mutant NefG2A, restored disease yields to levels acquired in the absence of exogenous EED protein. This effect was not observed with mutant Nef57 mimicking the Nef core, or with the lipid raft-retargeted fusion protein LAT-Nef. LATAA-Nef, a mutant defective in the lipid raft dealing with function, experienced the same anti-EED effect as WTNef. Cell fractionation and confocal imaging showed that, in the absence of Nef, EED primarily localized in membrane domains different from the lipid rafts. Upon co-expression with WTNef, NefG2A or LATAA-Nef, but not with Nef57 or LAT-Nef, EED was found to relocate into an insoluble portion along with Nef protein. Electron microscopy of HIV-Luc producer cells overexpressing EED showed significant less computer virus budding at the cell surface compared to control cells, and ectopic assembly and clustering of nuclear pore complexes within the cytoplasm. Conclusion Our data suggested that EED exerted an antiviral activity at the late stage of HIV-1 replication, which included genomic RNA packaging and computer virus assembly, resulting possibly Goserelin from a mistrafficking of viral genomic RNA (gRNA) or gRNA/Gag complex. Nef reversed the EED unfavorable effect on computer virus production, a function which required the integrity of the Nef N-terminal domain name, but not its N-myristoyl group. The antagonistic effect of Nef correlated with a cellular redistribution of both EED and Nef. Background EED protein, the human ortholog of the mouse embryonic ectoderm development ( em eed /em ) gene product, is a member of the superfamily of WD-40 repeat proteins and widely conserved em Polycomb /em group ( em Pc /em G) family of proteins [1-7]. The human EED protein, also called WAIT-1 (for WD protein associated with integrin cytoplasmic tails-1; [8]), can interact with the cytoplasmic tail of integrin 7 subunit, a domain which is usually involved in major integrin functions such as receptor affinity and signaling [9,10]. EED was also found to interact with three HIV-1 proteins, the Gag matrix protein MA [11], the integrase enzyme IN [12] and the Nef regulatory protein [13]. Although recognized as a nuclear factor, EED has been shown to shuttle between the nucleus and the plasma membrane [8], where it forms a complex with HIV-1 Nef releasing an EED-mediated transcriptional block [13]. The data obtained with Nef and EED were consistent with the known functions of em Pc /em G proteins, which participate in the maintenance of the silent state of chromatin in upper eukaryotes, such as in female X chromosome inactivation [14], and generally act as transcriptional repressors of homeotic genes (examined in [15-18]). They were also consistent with the finding that HIV-1 preferentially integrates into transcriptionally active regions of the host genome [19-22]. Thus, regions of cellular genome unoccupied by EED or EED-containing multiprotein complexes might be favored targets for proviral DNA integration. EED is a part of multiprotein edifices called Polycomb Repressive Complexes (PRCs) that are found in em Drosophila /em and in mammals [17]. Several types of PRCs have been recognized and generally called PRC1, PRC2 and PRC3 [23]. PRC2/3 contain at least five components, EED, EZH2, SUZ12, RbAp38 and AEBP2 [23-25]. Four isoforms of human EED have been recognized [24], due to option translation initiations at codons specific for Val1 (EED1), Val36 (EED2), Met95 (EED3) and Met110 (EED4), respectively, as aligned with the mouse EED sequence of 535 residues [5,7], and not to option splicing of the em eed /em transcript, as previously hypothesized Goserelin [11]. It is generally accepted that PRC3 complex contains the two shorter forms of EED (EED3, EED4), while PRC2 contains the longer EED1 form, and the intermediate EED2 form is present in another unique PRC complex [23]. However, a more dynamic and flexible view of the PRC composition has been proposed [17]. Because EED can interact with three major HIV-1 components, we wanted to investigate the interplay between EED and the computer virus in infected cells. We found that EED isoforms 3 and 4 (EED3/4) experienced only a moderate antiviral activity on infecting virions, whereas at the late phase of computer virus.