Multiple interfaces between a serine recombinase and an enhancer control site-specific DNA inversion

Area of Science:

• Molecular biology
• Genetics
• Biochemistry

Background:

• Serine recombinases, like Hin, are crucial for DNA manipulation.
• These enzymes are often regulated by complex protein-DNA interactions.
• The Hin recombinase system involves a remote enhancer element and Fis protein.

Purpose of the Study:

• To elucidate the mechanism by which the Fis protein and enhancer regulate Hin recombinase activity.
• To detail the structural interactions that promote the formation of the active Hin synaptic complex.
• To understand how enhancer-bound Fis controls DNA inversion and exchange.

Main Methods:

• Structural analysis of protein-DNA interactions.
• Biochemical assays to study DNA recombination.
• Investigating the role of Fis beta-hairpin arms in Hin complex formation.

Main Results:

• Fis dimers, via their beta-hairpin arms, contact Hin dimers, promoting their remodeling into a tetramer.
• A basic region on the Hin catalytic domain interacts with enhancer DNA to complete active tetramer assembly.
• These interactions reveal the enhancer's role in specifying DNA inversion and regulating exchange.

Conclusions:

• The Fis protein acts as a critical regulator of Hin recombinase assembly and activity.
• Specific protein-DNA contacts mediate the formation of the functional synaptic complex.
• This mechanism provides insight into how DNA inversion and exchange are precisely controlled.