Plant organellar DNA polymerases bypass thymine glycol using two conserved lysine residues

Noe Baruch-Torres, Junpei Yamamoto, Víctor Juárez-Quintero, Shigenori Iwai, Luis G. Brieba

Research output: Contribution to journalArticlepeer-review

Abstract

Plant organelles cope with endogenous DNA damaging agents, byproducts of respiration and photosynthesis, and exogenous agents like ultraviolet light. Plant organellar DNA polymerases (DNAPs) are not phylogenetically related to yeast and metazoan DNAPs and they harbor three insertions not present in any other DNAPs. Plant organellar DNAPs from Arabidopsis thaliana (AtPolIA and AtPolIB) are translesion synthesis (TLS) DNAPs able to bypass abasic sites, a lesion that poses a strong block to replicative polymerases. Besides abasic sites, reactive oxidative species and ionizing radiation react with thymine resulting in thymine glycol (Tg), a DNA adduct that is also a strong block to replication. Here, we report that AtPolIA and AtPolIB bypass Tg by inserting an adenine opposite the lesion and efficiently extend from a Tg-A base pair. The TLS ability of AtPolIB is mapped to two conserved lysine residues: K593 and K866. Residue K593 is situated in insertion 1 and K866 is in insertion 3. With basis on the location of both insertions on a structural model of AtPolIIB, we hypothesize that the two positively charged residues interact to form a clamp around the primer-template. In contrast with nuclear and bacterial replication, where lesion bypass involves an interplay between TLS and replicative DNA polymerases, we postulate that plant organellar DNAPs evolved to exert replicative and TLS activities.

Original languageEnglish (US)
Pages (from-to)1049-1059
Number of pages11
JournalBiochemical Journal
Volume477
Issue number5
DOIs
StatePublished - 2020
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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