Combinatorial recognition of a complex telomere repeat sequence by the Candida parapsilosis Cdc13AB heterodimer

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Telomeres protect chromosome ends but have unique structures in Candida species.
• Telomere-binding proteins are crucial for telomere function and maintenance.
• Understanding these proteins is key to comprehending telomere dynamics in Candida.

Purpose of the Study:

• To characterize the binding properties of Candida parapsilosis Cdc13A and Cdc13B.
• To elucidate the mechanism of telomere G-strand tail recognition by these proteins.
• To investigate the role of different protein domains in complex formation and DNA binding.

Main Methods:

• Electrophoretic mobility shift assay (EMSA) to assess DNA binding affinity.
• Crosslinking analysis to study protein-protein interactions.
• Domain mapping to identify functional regions within Cdc13A and Cdc13B.

Main Results:

• Cdc13A and Cdc13B form homo- and heterodimers.
• Only the Cdc13A/Cdc13B heterodimer exhibits high-affinity, sequence-specific binding to telomere G-tails.
• A combinatorial recognition mechanism involves subunits contacting distinct regions of the G-tail.
• The OB4 domains stabilize the heterodimer, while DBD domains contribute to DNA binding specificity.

Conclusions:

• The OB4 domains are critical for stable heterodimer formation.
• Cdc13A/Cdc13B employ a rare combinatorial mechanism for single-stranded DNA recognition.
• This study provides insights into the co-evolution of telomere DNA and binding proteins in Candida.