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Figure 6 | Virology Journal

Figure 6

From: Replication of porcine circoviruses

Figure 6

Model of the termination of rolling circle replication described by Novick in the nineties. Black: parental strand; Red: newly synthesized strand; Blue: newly synthesized strand during a second round of replication. Step 1: After the first round of replication, the REP complex bound on the 5' end would be situated behind the generated stem-loop. Step 2: the tyrosine (Y) of the unused sub-unit during the initiation might cleave the regenerated replication origin. It will (then bind to the 5' end of the newly synthesized strand. Step 3: the 3'OH free end generated during step 2 and belonging to the parental strand might then exert a nucleophilic attack on the tyrosylphosphodiester bridge generated during the initiation step. This reaction would lead to the release of a single stranded DNA. Step 4: the tyrosine previously involved in initiation of the replication attacks the cutting site of the newly synthesized strand. This reaction would generate a free 3'OH on the newly synthesized strand and a tyrosylphosphodiester bridge with a 12 mers oligonucleotide. Steps 5 and 6: the free 3'OH generated at step 4 can attack the tyrosylphosphodiester bridge generated at step 2, that would close the double stranded DNA and release an inactivated Rep homodimer due to the binding of one tyrosine to one oligonucleotide. Adapted from Microbiology and Molecular Biology Reviews 62(2), del Solar G et al, "Replication and control of circular bacterial plasmids." pages 434–464, Copyright© 1998 [5], with permission from American Society for Microbiology.

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