Figure 26-5: A model for P4 replication. Protein alpha binds to both ori1 and crr sites in oligomeric form and may cause looping of P4 DNA by protein-protein interactions. Protein alpha is thought to make RNA primers (arrowheads) both at the origin of replication (priming) and at the replicative forks for lagging strand priming (elongation). The Cnr protein, interacting with ?, prevents replication initiation by inhibiting either DNA looping or origin denaturation and priming.