A Meier-Gorlin syndrome mutation in a conserved C-terminal helix of Orc6 impedes origin recognition complex formation
Franziska Bleichert,
Maxim Balasov,
Igor Chesnokov,
Eva Nogales,
Michael R Botchan,
James M Berger
Affiliations
Franziska Bleichert
Miller Institute for Basic Research in Science, University of California, Berkeley, Berkeley, United States; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
Maxim Balasov
Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham School of Medicine, Birmingham, United States
Igor Chesnokov
Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham School of Medicine, Birmingham, United States
Eva Nogales
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States; Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, United States; Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
Michael R Botchan
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
James M Berger
Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
In eukaryotes, DNA replication requires the origin recognition complex (ORC), a six-subunit assembly that promotes replisome formation on chromosomal origins. Despite extant homology between certain subunits, the degree of structural and organizational overlap between budding yeast and metazoan ORC has been unclear. Using 3D electron microscopy, we determined the subunit organization of metazoan ORC, revealing that it adopts a global architecture very similar to the budding yeast complex. Bioinformatic analysis extends this conservation to Orc6, a subunit of somewhat enigmatic function. Unexpectedly, a mutation in the Orc6 C-terminus linked to Meier-Gorlin syndrome, a dwarfism disorder, impedes proper recruitment of Orc6 into ORC; biochemical studies reveal that this region of Orc6 associates with a previously uncharacterized domain of Orc3 and is required for ORC function and MCM2–7 loading in vivo. Together, our results suggest that Meier-Gorlin syndrome mutations in Orc6 impair the formation of ORC hexamers, interfering with appropriate ORC functions.
