Contact

  • Academic
    lasambel@stanford.edu
    University - Student Department: Chemical and Systems Biology Operations Position: Graduate

Additional Info

  • Mail Code: 5174

All Publications

  • Single-molecule imaging reveals the mechanism of bidirectional replication initiation in metazoa. Cell Terui, R., Berger, S. E., Sambel, L. A., Song, D., Chistol, G. 2024

    Abstract

    Metazoan genomes are copied bidirectionally from thousands of replication origins. Replication initiation entails the assembly and activation of two CMG helicases (Cdc45Mcm2-7GINS) at each origin. This requires several replication firing factors (including TopBP1, RecQL4, and DONSON) whose exact roles are still under debate. How two helicases are correctly assembled and activated at each origin is a long-standing question. By visualizing the recruitment of GINS, Cdc45, TopBP1, RecQL4, and DONSON in real time, we uncovered that replication initiation is surprisingly dynamic. First, TopBP1 transiently binds to the origin and dissociates before the start of DNA synthesis. Second, two Cdc45 are recruited together, even though Cdc45 alone cannot dimerize. Next, two copies of DONSON and two GINS simultaneously arrive at the origin, completing the assembly of two CMG helicases. Finally, RecQL4 is recruited to the CMGDONSONDONSONCMG complex and promotes DONSON dissociation and CMG activation via its ATPase activity.

    View details for DOI 10.1016/j.cell.2024.05.024

    View details for PubMedID 38866019

  • Single-Molecule Imaging Reveals the Mechanism of Bidirectional Replication Initiation in Metazoa. bioRxiv : the preprint server for biology Terui, R., Berger, S., Sambel, L., Song, D., Chistol, G. 2024

    Abstract

    Metazoan genomes are copied bidirectionally from thousands of replication origins. Replication initiation entails the assembly and activation of two CMG (Cdc45Mcm2-7GINS) helicases at each origin. This requires several firing factors (including TopBP1, RecQL4, DONSON) whose exact roles remain unclear. How two helicases are correctly assembled and activated at every single origin is a long-standing question. By visualizing the recruitment of GINS, Cdc45, TopBP1, RecQL4, and DONSON in real time, we uncovered a surprisingly dynamic picture of initiation. Firing factors transiently bind origins but do not travel with replisomes. Two Cdc45 simultaneously arrive at each origin and two GINS are recruited together, even though neither protein can dimerize. The synchronized delivery of two GINS is mediated by DONSON, which acts as a dimerization scaffold. We show that RecQL4 promotes DONSON dissociation and facilitates helicase activation. The high fidelity of bidirectional origin firing can be explained by a Hopfield-style kinetic proofreading mechanism.

    View details for DOI 10.1101/2024.03.28.587265

    View details for PubMedID 38585807