Understanding DNA Repair in Hyperthermophilic Archaea: Persistent Gaps and Other Reasons to Focus on the Fork

Figure 2

Fork breakage “collapse” in response to replication-blocking lesions. Adducts or other large, helix-distorting lesions (symbolized by X) block a polymerase molecule, inducing a certain degree of uncoupling and ssDNA exposure at the base of the fork. Cleavage by an appropriate single-strand-specific or structure-specific endonuclease can, for each case, generate dsDNA end that retains the lesion. The top strand in each DNA duplex is oriented with the 5′ end on left; free 3′ ends are represented by arrowheads, whereas broken lines indicate the rest of the chromosome. Carets (∧) locate the single cut that would be made by the indicated nuclease. For the cleavage preferences of archaeal Hef, Xpf, and Fen1/Xpg, see [36, 65, 66].

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