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Related Experiment Video

Updated: Sep 9, 2025

Generation and Assembly of Virus-Specific Nucleocapsids of the Respiratory Syncytial Virus

Generation and Assembly of Virus-Specific Nucleocapsids of the Respiratory Syncytial Virus

Published on: July 27, 2021

Structures of Nucleotide-Bound Redondovirus Rep Protein Link Conformation and Function.

Saira Montermoso, Kushol Gupta, Ruth Anne Pumroy

Biorxiv : the Preprint Server for Biology

|September 5, 2025

Summary

Researchers reveal the structure of a Redondovirus Rep protein, crucial for CRESS-DNA virus replication. This study uncovers key structural states and oligomeric assemblies, offering insights into viral DNA replication mechanisms.

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Area of Science:

Structural Biology
Virology
Biochemistry

Background:

Circular Rep-encoding single-stranded DNA (CRESS-DNA) viruses utilize Rep proteins for replication.
Rep proteins possess nicking, helicase, and DNA joining activities essential for viral genome replication.
The Redondoviridae family, a newly identified group of human-associated CRESS-DNA viruses, replicates in Entamoeba gingivalis.

Purpose of the Study:

To determine the first structures of a Rep protein from the Redondoviridae family.
To elucidate the structural mechanisms underlying Rep protein function in viral DNA replication.
To investigate the oligomeric states and their functional implications in CRESS-DNA virus replication.

Main Methods:

Cryo-electron microscopy (cryo-EM) was used to determine high-resolution structures.
Structures of Redondovirus Rep helicase were characterized in complex with ATPγS and ADP.
Biophysical analyses were employed to study Rep protein oligomerization.

Main Results:

Hexameric structures of Redondovirus Rep in ATP-bound (ATPγS) and post-hydrolysis (ADP) states were resolved.
The ADP-bound Rep exhibited a staircase arrangement of DNA-binding loops, critical for SF3 helicase models.
A head-to-tail dodecameric structure of ATPγS-bound Rep revealed ordered helicase and endonuclease domains.
Conserved residues suggest the dodecameric assembly is functionally relevant across many CRESS-DNA viruses.

Conclusions:

The structural and oligomeric insights into Redondovirus Rep provide a deeper understanding of CRESS-DNA virus replication.
The positioning of endonuclease domains in the hexamer and observed oligomerization states offer new functional perspectives.
This study lays the groundwork for further investigations into the Rep protein's role in viral lifecycle and potential therapeutic targeting.