Nuclear import of Cdc13 limits chromosomal capping.

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Cdc13 protein is vital for telomere maintenance and chromosome capping.
• Previous studies identified four OB-fold domains and one recruitment domain in Cdc13.
• The in vivo function of these sub-domains within the whole Cdc13 protein remained unclear.

Purpose of the Study:

• To investigate the specific roles of individual Cdc13 sub-domains in telomere capping in vivo.
• To elucidate the mechanisms governing Cdc13's nuclear import and retention.
• To understand how nucleo-cytoplasmic transport affects Cdc13 function.

Main Methods:

• Utilizing individual single domain deletions of Cdc13.
• Analyzing the impact of these deletions on telomere capping.
• Investigating the role of karyopherin Msn5 in Cdc13 nuclear localization.

Main Results:

• The OB2 domain of Cdc13 contains a nuclear localization signal essential for nuclear import and chromosome capping.
• Karyopherin Msn5 facilitates Cdc13 nuclear localization.
• Cdc13 binding to telomeres is required for its retention in the nucleus.
• Cdc13 homodimerization occurs independently of DNA binding and can happen in the cytoplasm.

Conclusions:

• Cdc13's nuclear abundance and capping function are significantly influenced by nucleo-cytoplasmic transport.
• Nuclear retention of Cdc13 is dependent on its DNA binding activity.
• The OB2 domain's nuclear localization signal is critical for Cdc13's role in chromosome capping.