A Dimerized Coiled-Coil Domain and an Adjoining Part of Geminin Interact with Two Sites on Cdt1 for Replication Inhibition

• Published in: Molecular cell 2004-07, Vol.15 (2), p.245-258
• Main Authors: Saxena, Sandeep, Yuan, Ping, Dhar, Suman Kumar, Senga, Takeshi, Takeda, David, Robinson, Howard, Kornbluth, Sally, Swaminathan, Kunchithapadam, Dutta, Anindya
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Cell Cycle Proteins - chemistry; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Crystallization; Dimerization; DNA Replication; DNA-Binding Proteins - metabolism; Geminin; Glutamic Acid - chemistry; Homeodomain Proteins - metabolism; Humans; Interphase; Molecular Sequence Data; Point Mutation - genetics; Protein Structure, Tertiary; S Phase; Selenomethionine - chemistry; Selenomethionine - metabolism; Xenopus laevis - metabolism; Xenopus Proteins
• ISSN: 1097-2765; 1097-4164
• DOI: 10.1016/j.molcel.2004.06.045

Geminin is a cellular protein that associates with Cdt1 and inhibits Mcm2-7 loading during S phase. It prevents multiple cycles of replication per cell cycle and prevents episome replication. It also directly inhibits the HoxA11 transcription factor. Here we report that geminin forms a parallel coiled-coil homodimer with atypical residues in the dimer interface. Point mutations that disrupt the dimerization abolish interaction with Cdt1 and inhibition of replication. An array of glutamic acid residues on the coiled-coil domain surface interacts with positive charges in the middle of Cdt1. An adjoining region interacts independently with the N-terminal 100 residues of Cdt1. Both interactions are essential for replication inhibition. The negative residues on the coiled-coil domain and a different part of geminin are also required for interaction with HoxA11. Therefore a rigid cylinder with negative surface charges is a critical component of a bipartite interaction interface between geminin and its cellular targets.