Moderate-throughput solution assay for integrase joining activity. Panel A. Principles of a solution assay to measure integrase joining activity by fluorescence. Labeling and symbols are as in Figure 1. FAM stands for carboxyfluorescein labeled DNA, a circle with B denotes a biotin modified 3' end in the target oligodeoxynucleotide. Panel B. Comparison of HIV-1 and ASV IN joining activities in Mg++ and Mn++. The dashed lines with squares show the activity of ASV IN and the solid lines with triangles show the activity of HIV-1 IN expressed as RFUs versus time. Filled and open symbols represent activity in Mn++ and Mg++, respectively. The inset shows results from the same experiment, after 40 min. and up to 180 min. incubation. Panel C. Comparison of the joining activity of ASV IN with the recessed versus the blunt-ended donor oligodeoxynucleotides in the presence of Mg++ (recessed donor oligodeoxynucleotide, dashed line with filled squares; blunt-ended donor oligodeoxynucleotide, solid line with filled circles).