Humanizing the yeast origin recognition complex

Clare S K Lee,Yuanliang Zhai,Vincy Ho,Bik-Kwoon Tye,Danny Leung,Jinsen Li,Wai Hei Lam,Ming Fung Cheung,Remo Rohs,Yongqian Zhao

doi:10.1038/s41467-020-20277-y

Abstract

The Origin Recognition Complex (ORC) is an evolutionarily conserved six-subunit protein complex that binds specific sites at many locations to coordinately replicate the entire eukaryote genome. Though highly conserved in structure, ORC’s selectivity for replication origins has diverged tremendously between yeasts and humans to adapt to vastly different life cycles. In this work, we demonstrate that the selectivity determinant of ORC for DNA binding lies in a 19-amino acid insertion helix in the Orc4 subunit, which is present in yeast but absent in human. Removal of this motif from Orc4 transforms the yeast ORC, which selects origins based on base-specific binding at defined locations, into one whose selectivity is dictated by chromatin landscape and afforded with plasticity, as reported for human. Notably, the altered yeast ORC has acquired an affinity for regions near transcriptional start sites (TSSs), which the human ORC also favors.

Highlights

The Origin Recognition Complex (ORC) is an evolutionarily conserved six-subunit protein complex that binds specific sites at many locations to coordinately replicate the entire eukaryote genome
In S. cerevisiae, autonomously replication sequences (ARSs) is characterized by a 17 bp ARS consensus sequence (ACS) embedded within ~125 bp DNA with a polar T-rich and A-rich base composition that is asymmetrically located between two wellpositioned nucleosomes[13]
Orc4-IHΔ strain is viable with activated S-phase checkpoint

Summary

Introduction

The Origin Recognition Complex (ORC) is an evolutionarily conserved six-subunit protein complex that binds specific sites at many locations to coordinately replicate the entire eukaryote genome. We demonstrate that the selectivity determinant of ORC for DNA binding lies in a 19-amino acid insertion helix in the Orc[4] subunit, which is present in yeast but absent in human. Removal of this motif from Orc[4] transforms the yeast ORC, which selects origins based on base-specific binding at defined locations, into one whose selectivity is dictated by chromatin landscape and afforded with plasticity, as reported for human. The bromo adjacent homology domain of Orc[1] is believed to play a role in tethering ORC to

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Conclusion