Modulation

Modulation of HLA-G and HLA-E antigens expression. In JEG-3 cells treated with proteasome inhibitors only a full length HLA-G1 protein is detected although all of alternatively spliced HLA-G transcripts are present. Accordingly a rapid degradation of truncated proteins is not responsible for their absence. Interestingly, in the transfectants proteasome inhibitor zLLL greatly enhanced expression of the HLA-G1 or -G2 transcripts as well as corresponding protein isoforms. HLA-G expression is regulated also by epigenetic mechanisms (DNA methylation, histone acetylation) and stress. The highest activation of HLA-G transcription was achieved by treatment of choriocarcinoma JAR and lymphoblastoid RAJI cell lines with demethylating agent 5-aza-2´-deoxycytidine. Treatment of these cells with histone deacetylase inhibitors (butyrate or valproic acid) also enhanced HLA-G transcription. Relatively high increase of HLA-G transcription was detected in JAR cells exposed to heat shock treatment, where a profound expression of HLA-G6 transcript was found.