Crystallization and preliminary crystallographic study of triple-helical DNA

Area of Science:

• Structural Biology
• Crystallography
• Molecular Biology

Background:

• DNA can adopt various structural forms beyond the canonical double helix.
• Understanding these alternative structures is crucial for comprehending DNA function and regulation.

Purpose of the Study:

• To determine the three-dimensional structure of a novel DNA construct.
• To investigate the formation of DNA duplex and triplex structures in a crystalline state.

Main Methods:

• Single crystals of the DNA construct d(CTCCT(S)CCGCGCG).d(CGCGCGGAG) were grown using vapor-diffusion.
• X-ray diffraction data were collected at a synchrotron beamline to a resolution of 1.8 A.

Main Results:

• Tetragonal crystals (space group P4(2)) with unit-cell parameters a = b = 53.8 A, c = 43.1 A were obtained.
• The crystal structure revealed that the DNA construct forms a duplex at one end and a triplex at the other.
• Non-crystallographic twofold symmetry relates the two halves of the asymmetric unit.

Conclusions:

• The crystallized DNA construct exhibits a unique hybrid duplex-triplex architecture.
• This structural characterization provides insights into the formation and stability of DNA triplexes.
• The findings contribute to the broader understanding of DNA structural diversity and its implications.