Figure 2. IN 3′ processing activities.

(A) Schematic of blunt-ended vDNA substrate processed by IN adjacent to the conserved CA 3′ dinucleotide (vertical arrowhead). Positions of ³²P label are shown by *. (B) Polyacrylamide sequencing gel of products of HIV-1, MMTV, and Rev-A IN 3′ processing reactions; Mn²⁺, Mg²⁺, and glycerol were included as indicated. The positions of the starting substrates (30 bp for HIV-1 IN; 32 bp for MMTV and Rev-A), the simple dinucleotide cleavage products (pGpT_OH for HIV-1 and pTpT_OH for MMTV and Rev-A), and form I and form II cleavage products are indicated. IN proteins were omitted from the initial reaction in each set of five reactions. (C) Mn²⁺ and Mg²⁺-dependent 3′ processing activities expressed as percentage of product formation ± standard error of the mean (SEM) for three independent experiments. Asterisks indicate P values <0.05 by paired t-test.