Distant sequence regions of JBP1 contribute to J-DNA binding

Area of Science:

• Molecular Biology
• Epigenetics
• Biochemistry

Background:

• Base-J (β-D-glucopyranosyloxymethyluracil) is a unique DNA modification found in kinetoplastids, replacing thymine.
• Base-J biosynthesis and maintenance rely on the base-J-binding protein 1 (JBP1), which possesses thymidine hydroxylase and J-DNA-binding domains (JDBD).
• The precise mechanism by which JBP1 ensures accurate base-J replication during DNA synthesis remains incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanism of JBP1's interaction with J-DNA.
• To determine the binding mode of the J-DNA-binding domain (JDBD) to J-DNA.
• To investigate the role of the JBP1 N-terminus in DNA binding.

Main Methods:

• X-ray crystallography of the JDBD.
• Molecular dynamics simulations.
• Computational docking studies.
• Site-directed mutagenesis experiments.

Main Results:

• A crystal structure of the JDBD, including a DNA-contacting loop, was determined.
• Computational models proposed JDBD recognition and binding modes to J-DNA.
• Mutagenesis experiments confirmed the contribution of the JBP1 N-terminus to DNA binding.

Conclusions:

• The study provides a detailed model for JDBD binding to J-DNA.
• The flexible JBP1 N-terminus plays a crucial role in DNA binding.
• Further experimental determination of a high-resolution JBP1:J-DNA complex is needed to fully understand base-J replication.