Fig 4.

Competition experiments with mutations at codon E138 in MT-2 cells monitored by AS-PCR. The data are representative of means ± the SEM of three independent experiments. (A to D) Results of competition experiments using E138A, E138G, E138K, E138Q, and E138R mutations. (A) Competition experiments performed without altering the dNTP concentration. (B) 1.5 mM hydroxyurea (HU) was added to the medium. (C) 0.65 mM deoxynucleosides (dN) were added to the medium. (D) Fold change in the proportions of individual substitutions at the end of the competition experiment. Bars: ▧, fold change with the addition of HU; □, fold change with the addition of deoxynucleosides. (E to H) Results of competition experiments using E138K virus and wild type. Lines: solid line, wild type; dashed line, E138K. “1 + s” is the relative viral fitness with the SEM noted. (E) Competition experiment performed without altering the dNTP concentration. (F) 1.5 mM hydroxyurea (HU) was added to the medium. (G) 0.65 mM deoxynucleoside (dN) was added to the medium. (H) Both 1.5 mM HU and 0.65 mM dN were added to the medium. Note that this combination caused a minor decrease in MT-2 cell replication.