Comment on “The [4Fe4S] cluster of human DNA primase functions as a redox switch using DNA charge transport”

Abstract

O’Brien et al. (Research Articles, 24 February 2017, eaag1789) proposed a novel mechanism of primase function based on redox activity of the iron-sulfur cluster buried inside the C-terminal domain of the large primase subunit (p58C). Serious problems in the experimental design and data interpretation raise concerns about the validity of the conclusions.

Yeast require redox switching in DNA primase

“…Aromatic tyrosines spaced ≤15 Å apart can facilitate microsecond electron transfer (20, 21) in protein, possibly through formation of hopping intermediates. Despite previous arguments that structural differences in yeast and human primase preclude a general redox role for these residues (37), the electrochemical and biological data unequivocally demonstrate that the electron-transfer pathway is conserved. Electrochemical attenuation of the p58C redox signal on DNA and lethality in yeast due to a single-residue redox-pathway mutation suggest a more significant role than the contributions of these tyrosines to any network of p58C/substrate hydrogen bonds (13).…”

Response to Comments on “The [4Fe4S] cluster of human DNA primase functions as a redox switch using DNA charge transport”

“…Neither Baranovskiy et al (2) nor Pellegrini (3) directly dispute the electrochemical observations of charge transport through the DNA substrate to the iron-sulfur cluster of our p58 construct, nor do they dispute its inhibition by mutation of each of the three relevant tyrosine residues. Rather, they question the path for electron transfer through primase on the basis of differences in structures of p58C, the primase domain containing the [4Fe4S] cluster (4–6).…”

A comprehensive mechanistic model of iron metabolism inSaccharomyces cerevisiae

“…This is ironic since the biochemical roles of those ISCs are largely unknown. Such clusters might pass charge along the DNA for longrange signaling 230,231 but this is controversial 232 and perhaps simplistic given the diversity of nuclear enzymes that contain these clusters. 5.…”