HIV-1 modulates the interferon-induced antiviral host mechanisms, protein kinase R and 2',5'-oligoadenylate synthesis. Structure in blue represents generic retrovirus transcript with highly structured 5' UTR. Left panel illustrates the 2',5'-oligoadenylate synthesis (2-5OAS) pathway that typically results in RNAseL activation and cleavage of viral double-stranded RNA. Vertical lines within RNaseL indicate ankyrin repeats. Right panel illustrates the double-stranded RNA-inducible PKR pathway. PKR is depicted by the green N-terminal double-stranded RNA binding motif (dsRBM) with central domain and C-terminal kinase domain depicted by pink line. Tat transactivation response element (TAR) RNA binding protein (TRBP), Tat, and 2-5OAS proteins are marked. Tat 86 and Tat 72 indicate the 86 amino acid and 72 amino acid isoforms of HIV-1 Tat. Circles labeled with P indicate phosphorylation. Black arrows indicate normal progression through the pathway. Red block arrows and text boxes outlined in red indicate points of interaction and modulation by HIV-1.