The mechanism of universal replication initiation dependent on G4/RNA-DNA hybrids.

We found that guanine quadruplex (G4)/RNA-DNA hybrids, a typical non-B-type nucleic acid structure, involved in two important aspects of DNA replication: inhibition of replication initiation via chromosomal higher-order structure formation and positive signaling of replication initiation. Recognition of G4 by the Rif1 protein, which is evolutionarily conserved from yeast to human, is important. We have elucidated in detail the domains required for G4 recognition by Rif1 and their interactions, and submitted a model for the formation of chromatin higher-order structures by Rif1. We also reproduced replication initiation from G4/RNA-DNA hybrids in vitro and verified the importance of G4 structure in replication initiation. In this study, we will extend these findings to elucidate the higher-order structure of the Rif1-G4 complex, the mechanism of replication timing control by the nuclear chromosome structure formed by the complex, and the mechanism of universal replication initiation dependent on G4/RNA-DNA hybrids. Furthermore, we will complete a novel method to detect intracellular G4, determine the intracellular profile of G4, and elucidate its diverse functions.