CpG dinucleotides introduced into gag can inhibit HIV-1 gene expression by modulating pre-mRNA splicing

Progressively longer regions of the gag gene sequence in HIV-1 were codon-optimized, which introduced 11, 18 or 26 CpGs (CM22-165: codon-optimized gag from nucleotide 22 to 165, adding 11 CpGs; CM22-261: 18 CpGs; CM22-378: 26 CpGs). Two independent transfections of HeLa cells with plasmids encoding HIV-1 provirus were performed for each of the codon-optimized HIV-1 versions as well as the un-optimized, wildtype version of HIV-1.