Book of Abstracts: Albany 2007

category image Albany 2007
Conversation 15
June 19-23 2007

Structural Studies of Mcm10, An Essential Eukaryotic Replication Initiation Factor

Initiation of DNA replication in eukaryotes is a tightly regulated process to ensure that the genome is replicated only once and at the proper time in the cell cycle. During initiation, a large number of proteins are mobilized to assemble at origins of replication, unwind the DNA duplex, and assemble into the functional replisome--the multiprotein machinery necessary to synthesize DNA at the replication fork. However, the specific functions and physical properties of many of these proteins, and thus the molecular mechanism of replication initiation, are unknown.  Studies using Xenopus extracts have shown that Mcm10 is one of the first proteins to associate with pre-replicative complexes at replication origins at the onset of S-phase, and is required for subsequent loading of downstream factors onto chromatin, including the helicase co-factor Cdc45. In order to gain a mechanistic understanding of Mcm10?s precise role, we are characterizing the structure and biochemical properties of vertebrate Mcm10. Here, we report the crystal structure of a highly conserved region of Mcm10 from Xenopus laevis. The structure shows two classic DNA binding motifs indicative of both single-stranded (ss) and double-stranded (ds) DNA binding. Crystallographic and biochemical analyses provide a model for how Mcm10 engages ss- and dsDNA at discrete but adjacent sites on the protein. These data suggest that Mcm10 might play a role in melting origin DNA and might preferentially associate with an emerging replication fork. 

Eric M. Warren1
Audrey H. Metz1
Antonin V. Tutter2
Johannes C. Walter2and
Brandt F. Eichman1

Dept of Biological Sci., 1 and
Ctr for Structural Biology,
Vanderbilt University,
Nashville TN 37232-0146, USA

Dept of Biological Chemistry and
Molecular Pharmacology2,
Harvard Medical School,
240 Longwood Avenue,
Boston MA 02115, USA

Phone: (615)936-5233
Fax: (615)343-6707
Email: eric.m.warren@vanderbilt.edu