Genetic Control of Replication through N1-methyladenine in Human Cells.
N1-methyl adenine (1-MeA) is formed in DNA by reaction with alkylating agents and naturally occurring methyl halides. The 1-MeA lesion impairs Watson-Crick base pairing and blocks normal DNA replication. Here we identify the translesion synthesis (TLS) DNA polymerases (Pols) required for replicating through 1-MeA in human cells and show that TLS through this lesion is mediated via three different pathways in which Pols ι and θ function in one pathway and Pols η and ζ, respectively, function in the other two pathways. Our biochemical studies indicate that in the Polι/Polθ pathway, Polι would carry out nucleotide insertion opposite 1-MeA from which Polθ would extend synthesis. In the Polη pathway, this Pol alone would function at both the nucleotide insertion and extension steps of TLS, and in the third pathway, Polζ would extend from the nucleotide inserted opposite 1-MeA by an as yet unidentified Pol. Whereas by pushing 1-MeA into the syn conformation and by forming Hoogsteen base pair with the T residue, Polι would carry out TLS opposite 1-MeA, the ability of Polη to replicate through 1-MeA suggests that despite its need for Watson-Crick hydrogen bonding, Polη can stabilize the adduct in its active site. Remarkably, even though Pols η and ι are quite error-prone at inserting nucleotides opposite 1-MeA, TLS opposite this lesion in human cells occurs in a highly error-free fashion. This suggests that the in vivo fidelity of TLS Pols is regulated by factors such as post-translational modifications, protein-protein interactions, and possibly others.
From the Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Blvd., Galveston, Texas 77555-1061.
Juan
J
Conde
From the Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Blvd., Galveston, Texas 77555-1061.
Jung-Hoon
JH
Yoon
From the Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Blvd., Galveston, Texas 77555-1061.
Jayati
J
Roy Choudhury
From the Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Blvd., Galveston, Texas 77555-1061.
Louise
L
Prakash
From the Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, 301 University Blvd., Galveston, Texas 77555-1061 s.prakash@utmb.edu.
Satya
S
Prakash
D000225:Adenine / Q000031:analogs & derivatives* / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics*; D006801:Humans
D000225:Adenine
DNA; DNA damage; DNA polymerase; DNA polymerase eta; DNA polymerase iota; DNA polymerase theta; DNA replication; DNA synthesis; N1-methyladenine; translesion synthesis in human cells