RESUMO
Human endogenous retrovirus-K (HERV-K) Gag protein is produced by both Tera 1 and PA-1 (ovarian teratocarcinoma) cells, but only Tera 1 cells release the protein in the form of particles. It was unclear how Gag production was regulated in these cell types. Although both Tera 1 and PA-1 cells express Gag, demethylation upon treatment with 5-azacytidine (5-AZC) or exposure to the chromatin-modifying agent n-butyrate resulted in an increase in Gag protein levels only in Tera 1 cells. Consistent with this cell type-specific overexpression of Gag in response to demethylation, exposure to 5-AZC caused undermethylation of the gag gene and adjacent 5'LTR only in Tera 1 but not PA-1 or Raji cells. Similarly and importantly, undermethylation of gag sequences and expression of Gag were also correlated in primary human testicular tumours. These results therefore suggest that endogenous retroviral elements are subject to regulation through the methylation of CpG dinucleotides.
Assuntos
Produtos do Gene gag/metabolismo , Retroelementos , Azacitidina/farmacologia , Butiratos/farmacologia , Ácido Butírico , Metilação de DNA , DNA Viral/análise , Feminino , Produtos do Gene gag/genética , Humanos , Masculino , Metilação , Neoplasias Ovarianas/metabolismo , Neoplasias Ovarianas/patologia , Teratocarcinoma/metabolismo , Teratocarcinoma/patologia , Neoplasias Testiculares/patologia , Neoplasias Testiculares/virologia , Células Tumorais CultivadasRESUMO
We have previously shown by far-Western blotting that the Epstein-Barr virus nuclear antigen 2 (EBNA-2) both binds to a cellular protein of 130 kDa and histone H1, with the complex between EBNA-2 and p130 being tighter than between EBNA-2 and histone H1. Here we demonstrate that the N terminus of EBNA-2, which was previously shown to be necessary for transformation of B lymphocytes by EBNA-2, is essential for binding to p130. We further show data indicating that the binding of EBNA-2 to histone H1 appears not to be mediated exclusively via the basic Arg-Gly rich region in the C-terminal part of EBNA-2. With a MAb directed against the Trp-Trp322-Pro (WWP) motif of EBNA-2, which is known to be essential for the interaction of EBNA-2 with the cellular factor RBPJkappa/CBF1, we could inhibit the DNA binding of EBNA-2, providing further evidence that this region of EBNA-2 forms direct contact with RBPJkappa/CBF1.
