Origin flexibility governs robust ssDNA engagement by the DnaA initiator.

Authors

Nanato Kiyohara, Yasutaka Wakasugi, Kohei Ihara, Ayaka Kubaru, Sena Maruki, Naho Kojima, Sachiko Yoshitomi, Tsutomu Katayama, Shogo Ozaki

Published in

Proceedings of the National Academy of Sciences of the United States of America. Volume 123. Issue 38. Pages e2615469123. Sep 22, 2026. Epub Sep 15, 2026.

Abstract

In model bacteria, initiation of chromosome replication requires engagement of single-stranded DNA by oligomers of the DnaA-family initiator assembled within the origin DNA. Although arrays of double-strand motifs recognized by DnaA are a general feature of the origins, the DnaA-binding single-strand elements are elucidated in only a limited number of species, and the mechanical principles governing their recognition remain elusive. Using the Alphaproteobacterium Caulobacter crescentus, we identify a previously uncharacterized GA-rich single-stranded element in the origin that directly engages DnaA oligomers and is essential for robust initiation. This element is positioned at a subkilobase distance from the DnaA oligomerization region and is brought into proximity through dynamic structural rearrangements. Moreover, DnaA oligomers exhibit an unexpectedly broad yet constrained capacity to accommodate single-stranded sequence variation. These findings provide the molecular basis for origin plasticity, highlighting how origins can diverge while preserving initiation logic.

PMID:
42743294
Bibliographic data and abstract were imported from PubMed on 16 Sep 2026.

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