Direct pairing of homologous DNA double helices may involve the B-to-C form transition

TL;DR

This paper explores how the transition from B-DNA to C-DNA form may facilitate direct homologous pairing of DNA duplexes, potentially explaining mechanisms of chromosomal region association without recombination.

Contribution

It proposes that B-to-C DNA form transition lowers energy barriers, enabling homologous DNA pairing, a novel insight into DNA recognition mechanisms.

Findings

C-DNA duplexes pair more readily than B-DNA due to structural features.

The wide and shallow major groove of C-DNA facilitates initial homologous contacts.

The B-to-C transition may play a key role in recombination-independent DNA pairing.

Abstract

In many organisms, homologous (or repetitive) chromosomal regions can associate or/and undergo concerted epigenetic changes in the absence of DNA breakage and recombination. The direct specific pairing of DNA duplexes with similar nucleotide sequences represents an attractive mechanism for recognizing such regions. Whereas the pairing of B-DNA duplexes may involve a large energy barrier, C-DNA duplexes are expected to pair much more readily. This unique feature of C-DNA is largely due to the fact that its major groove is wide and very shallow, permitting almost perfect initial homologous contacts between two duplexes without clashing. Overall, the conjectured role of C-DNA in recombination-independent pairing should revive the efforts to understand its structure and function in the cell.