Unmodified oligonucleotides

2-F-dI phosphoramidite was purchased from Glen Research. Unmodified oligonucleotides and 6-carboxyfluorescein (FAM)-labeled oligonucleotide primers were purchased from Integrated DNA Technologies (IDT). The 15- and 36-mer peptides were purchased from New England Peptides. C₁₈ Sep-Pak columns were purchased from Waters. Other chemical reagents were from Sigma-Aldrich. hpol η (catalytic core of 1–432 amino acids) and hpol κ (19–526 amino acids) were expressed in E. coli and purified as previously reported (53 (link), 54 (link)). Unlabeled dNTPs and UDG were purchased from New England Biolabs. Micro Biospin-6 columns were purchased from Bio-Rad.

DNA origami structures
were assembled in a single folding reaction carried out in a test
tube (AB0620, ThermoFisher Scientific) with 10 μL of folding
mixture containing 10 nM M13mp18 scaffold DNA (New England Biolabs),
100 nM unmodified oligonucleotides (Integrated DNA technologies),
either 100 nM biotin-modified oligonucleotides (Biomers) for direct
hybridization to the DNA origami tile (H57-dSAv-NL, H57-tSAv-NL) or
500 nM biotinylated oligonucleotides (Biomers) for external hybridization
(H57-dSAv, H57-tSAv) and folding buffer (5 mM Tris (AM9855G, ThermoFisher
Scientific), 50 mM NaCl (AM9759, ThermoFisher Scientific), 1 mM EDTA
(AM9260G, ThermoFisher Scientific), 12.5 mM MgCl2) (AM9530G, ThermoFisher
Scientific)). Oligonucleotide sequences are shown in the Supporting
Information Appendix, Tables S13–S15. At the site chosen for ligand attachment, a staple strand was elongated
at its 3′-end with 21 bases (H57-DNA, H57-PNA, H57-mSAv, H57-dSAv,
H57-tSAv). At sites chosen for cholesterol anchor attachment, staple
strands were elongated at the 5′-end with 25 bases, respectively.
DNA origami were annealed using a thermal protocol (90 °C, 15
min; 90 °C – 4 °C, 1 °C min^–1; 4 °C, 6 h) and purified using 100 kDa Amicon Ultra centrifugal
filters (UFC510096, Merck). DNA origami were stored up to 4 weeks
at −20 °C.