Abstract
Enzymes and Reactions at the Eukaryotic DNA Replication Fork
Highlights
Synthesis of the Leading Strand The separation of parental DNA strands determines the direction of movement of the replication fork
Okazaki fragment intermediates consist of initiator RNAs averaging about 10 nucleotides in length, extended with 10 –20 additional deoxyribonucleotides [31]
Because Okazaki fragment intermediates are made in the absence of ATP, and replication factor C (RFC) requires ATP for polymerase switching, the deoxyribonucleotides of the intermediates appear to be added by DNA pol ␣ prior to the switch
Summary
Removal of the junctional ribonucleotide is generally inhibited by an upstream primer This suggests that the initiator RNA removed by RNase H1 dissociates before FEN1/RTH1-directed cleavage of the junctional ribonucleotide. The free unannealed strand can drift through the archway, and the rest of the substrate would dissociate from the cleft Both exo- and endonucleolytic mechanisms of initiator RNA processing allow for the removal of some of the DNA downstream of the initiator RNA. This could occur through a nick translation process involving the exonucleolytic action of FEN1/RTH1. It could explain why DNA pol ␣ [53] had no need for 3Ј–5Јexonuclease activity
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