Date of Award

Spring 2002

Document Type

Restricted Thesis

Terms of Use

© 2002 Lenette Lu. All rights reserved. Access to this work is restricted to users within the Swarthmore College network and may only be used for non-commercial, educational, and research purposes. Sharing with users outside of the Swarthmore College network is expressly prohibited. For all other uses, including reproduction and distribution, please contact the copyright holder.

Degree Name

Bachelor of Arts


Biology Department

First Advisor

Elizabeth Ann Vallen


SID2 is the S. cerevisiae ortholog of CDT1, an essential gene required for origin licensing in DNA replication. An allele of SID2, sid2-1, was originally identified in a screen for mutants synthetically lethal with deletion of Sic1, a Clb-Cdc28 kinase inhibitor. Here, field inversion gel electrophoresis conducted on chromosomes isolated from sid2-21 cells indicate that they arrest with replication forks or bubbles. A two hybrid library screen of protein-protein interactions involving both wild-type and mutant forms of Sid2p isolated many proteins that interact with Sid2p. However, this analysis appears to have failed to give insight into its biologically relevant interacting partners, as the proteins identified have a variety of functions. The S. pombe homologs of Sid2p and Cdc6p, Cdtlp and Cdc18p, have been shown to co-immunoprecipitate. However, a direct two hybrid test of physical interactions between Sid2p and Cdc6p indicate that Sid2p may function in a manner that does not involve physical interaction with Cdc6p. These results indicate that although SID2 is the S. cerevisiae ortholog of CDT1, the specific mechanisms underlying its role in DNA replication may diverge.