Shared Active Site Architecture between the Large Subunit of Eukaryotic Primase and DNA PhotolyaseReportar como inadecuado

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DNA synthesis during replication relies on RNA primers synthesised by the primase, a specialised DNA-dependent RNA polymerase that can initiate nucleic acid synthesis de novo. In archaeal and eukaryotic organisms, the primase is a heterodimeric enzyme resulting from the constitutive association of a small PriS and large PriL subunit. The ability of the primase to initiate synthesis of an RNA primer depends on a conserved Fe-S domain at the C-terminus of PriL PriL-CTD. However, the critical role of the PriL-CTD in the catalytic mechanism of initiation is not understood.

Methodology-Principal Findings

Here we report the crystal structure of the yeast PriL-CTD at 1.55 Å resolution. The structure reveals that the PriL-CTD folds in two largely independent alpha-helical domains joined at their interface by a 4Fe-4S cluster. The larger N-terminal domain represents the most conserved portion of the PriL-CTD, whereas the smaller C-terminal domain is largely absent in archaeal PriL. Unexpectedly, the N-terminal domain reveals a striking structural similarity with the active site region of the DNA photolyase-cryptochrome family of flavoproteins. The region of similarity includes PriL-CTD residues that are known to be essential for initiation of RNA primer synthesis by the primase.


Our study reports the first crystallographic model of the conserved Fe-S domain of the archaeal-eukaryotic primase. The structural comparison with a cryptochrome protein bound to flavin adenine dinucleotide and single-stranded DNA provides important insight into the mechanism of RNA primer synthesis by the primase.

Autor: Ludovic Sauguet, Sebastian Klinge, Rajika L. Perera, Joseph D. Maman, Luca Pellegrini



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