Telomeric G-Quadruplexes: From Human to Tetrahymena Repeats

Area of Science:

• Biochemistry
• Genomics
• Molecular Biology

Background:

• Human telomeric DNA sequences (TTAGGG) and protozoal telomeric sequences (TTGGGG) exhibit a single purine base difference.
• G-quadruplexes are nucleic acid structures formed from guanine-rich sequences.
• These structures play roles in various cellular processes, including DNA replication and transcription.

Purpose of the Study:

• To analyze and compare G-quadruplexes formed from human and protozoal telomeric repeats and their derivatives.
• To investigate the impact of systematic adenine to guanine base substitutions on G-quadruplex formation, stability, and topology.
• To understand the implications of G-quadruplex structural variability for genomic functions.

Main Methods:

• Synthesis of human telomeric DNA sequences with systematic adenine to guanine substitutions, yielding Tetrahymena repeats.
• Analysis of G-quadruplex formation using biophysical techniques.
• Comparison of structural properties and stability of wild-type and substituted sequences.

Main Results:

• Base substitutions did not prevent G-quadruplex formation.
• Increased substitutions led to enhanced stability of the G-quadruplex derivatives.
• Sequence imperfections found in the analyzed derivatives are also present in human and Tetrahymena genomes.
• Substitutions may influence G-quadruplex topology.

Conclusions:

• G-quadruplex formation is robust to specific base substitutions found in telomeric sequences.
• Base substitutions can modulate G-quadruplex stability and topology, with potential implications for genome stability.
• Understanding these structural variations is crucial for comprehending G-quadruplex roles in biological systems.