The Xer activation factor of TLCΦ expands the possibilities for Xer recombination

Solange Miele (1, 2) , James Iain Provan (1, 2) , Justine Vergne (1, 2) , Christophe Possoz (1, 2) , Françoise Ochsenbein (1) , François-Xavier Barre (1, 3)

1 I2BC - Institut de Biologie Intégrative de la Cellule
2 DBG - Département Biologie des Génomes
3 EMC2 - Evolution et maintenance des chromosomes circulaires

The chromosome dimer resolution machinery of bacteria is generally composed of two tyrosine recombinases, XerC and XerD. They resolve chromosome dimers by adding a crossover between sister copies of a specific site, dif. The reaction depends on a cell division protein, FtsK, which activates XerD by protein-protein interactions. The toxin-linked cryptic satellite phage (TLC) of Vibrio cholerae, which participates in the emergence of cholera epidemic strains, carries a dif-like attachment site (attP). TLC exploits the Xer machinery to integrate into the dif site of its host chromosomes. The TLC integration reaction escapes the control of FtsK because TLC encodes for its own XerD-activation factor, XafT. Additionally, TLC attP is a poor substrate for XerD binding, in apparent contradiction with the high integration efficiency of the phage. Here, we present a sequencing-based methodology to analyse the integration and excision efficiency of thousands of synthetic mini-TLC plasmids with differing attP sites in vivo. This methodology is applicable to the finegrained analyses of DNA transactions on a wider scale. In addition, we compared the efficiency with which XafT and the XerD-activation domain of FtsK drive recombination reactions in vitro. Our results suggest that XafT not only activates XerD-catalysis but also helps form and/or stabilize synaptic complexes between imperfect Xer recombination sites.

Domaines: Sciences du Vivant [q-bio]

Solange Miele, James Iain Provan, Justine Vergne, Christophe Possoz, Françoise Ochsenbein, et al.. The Xer activation factor of TLCΦ expands the possibilities for Xer recombination. Nucleic Acids Research, 2022, 50, pp.6368 - 6383. ⟨10.1093/nar/gkac429⟩. ⟨hal-03872179⟩