Yra1 is required for S phase entry and affects Dia2 binding to replication origins

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• The F-box protein Dia2 is essential for DNA replication and maintaining genomic stability in Saccharomyces cerevisiae.
• Yra1 is known as a transcription-coupled mRNA export protein.

Purpose of the Study:

• To investigate the functional relationship between Dia2 and Yra1.
• To determine if Yra1 has roles beyond mRNA export, particularly in DNA replication.

Main Methods:

• Affinity purification to identify Dia2 interaction partners.
• Analysis of yeast mutants (yra1) for sensitivity to DIA2 expression levels.
• Chromatin association and replication origin binding assays.
• Co-immunoprecipitation with DNA polymerase delta subunit Hys2.
• Characterization of a Yra1 C-terminal deletion mutant.

Main Results:

• Yra1 was identified as a Dia2 interaction partner.
• Yra1 associates with chromatin and replication origins, similar to Dia2.
• A Yra1 mutant lacking the Dia2-interacting C-terminus is temperature-sensitive and fails to enter S phase.
• This S phase defect is specific to the Yra1-Dia2 interaction, as other mRNA export mutants do not show these phenotypes.
• Compromised Yra1-Dia2 association reduces Dia2 binding to replication origins.

Conclusions:

• Yra1 plays a critical role in DNA replication, independent of its established function in mRNA export.
• The interaction between Yra1 and Dia2 is essential for proper S phase entry.
• Yra1 may facilitate Dia2 recruitment to chromatin, contributing to its function in DNA replication.