Fig. 4.

Functionally important differences between the PCNA/FEN1/DNA and 9-1-1/FEN1/DNA complexes. PCNA and 9-1-1 serve different functions and, as a consequence, display different modes of association to FEN1 and DNA. The DNA and FEN1 are more tilted in 9Δ-1-1 complex than in the corresponding PCNA complex. The 9Δ-1-1 ring shows more interactions with the upstream duplex and stabilizes DNA passing through the ring. Such differences at the structural level may translate into functional differences in the ways these complexes engage at the replication fork. PCNA/DNA interactions are linked to processive and mobile sliding, whereas the tighter 9-1-1 interactions would be consistent with a scaffolding role for 9-1-1.