分子生物学：抗噬菌体逆转录酶以蛋白质为模板合成二核苷酸重复DNA

Pujuan Deng1,2†, Hyunbin Lee1,2†, Carlo Armijo1,3†, Haoqing Wang4, Alex Gao1,2* Defense-associated reverse transcriptases (DRTs) are widespread bacterial antiphage systems that use unconventional mechanisms of polynucleotide synthesis. We show that DRT3, which comprises two distinct RTs (Drt3a and Drt3b) and a noncoding RNA (ncRNA), synthesizes alternating poly(GT/AC) double-stranded DNA. Cryo–electron microscopy structures at 2.6-angstrom resolution reveal a D3-symmetric 6:6:6 complex of Drt3a, Drt3b, and ncRNA. Drt3a produces the poly(GT) strand using a conserved ACACAC template within the ncRNA. Notably, Drt3b synthesizes a complementary, protein-primed poly(AC) strand in the complete absence of a nucleic acid template, using conserved active site residues specific to Drt3b to enforce precise base alternation. …