Phosphorylation of AZT-resistant human immunodeficiency virus type 1 reverse transcriptase by casein kinase II in vitro: Effects on inhibitor sensitivity

Casein kinase II (CW) phosphorylates wild-type (WT) recombinant reverse tra nscriptase (RT) mainly in the p66 subunit in vitro. Phosphorylation of T215 F RT and D67N/K70R/T215F/K219Q RT (AZT-resistant RT) in vitro increases dis crimination against AZTTP 2.5- and 3.6-fold, respectively. This in vitro re sistance can be reversed by treatment of phosphorylated AZT-resistant RT wi th phosphatase. Phosphorylation has no effect on WT RT. Terminal transferas e activity of RT is selectively suppressed on phosphorylated AZT-resistant RT. Resistance to phosphonoformic acid (PFA, foscarnet) increases 3-fold up on phosphorylation of, AZT-resistant RT. Although T215, the most important residue for AZT-resistance, is part of a CKII consensus target site, serine s are primarily phosphorylated relative to threonines. Mutational analysis shows that phosphorylation can be reduced to 10% that of WT when amino-acid changes are introduced both in the "fingers" subdomain and motif D. These results suggest that phosphorylation of RT might be one factor involved in drug resistance in Dice. (C) 2000 Academic Press.