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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 endonuclease and NTP-dependent helicase activities.
  • Redondoviridae is a newly identified family of human-associated CRESS-DNA viruses.

Purpose of the Study:

  • To determine the structures of a Redondovirus Rep protein.
  • To elucidate the mechanism of Rep protein function in viral DNA replication.
  • To investigate the oligomeric states and functional implications of Rep protein assemblies.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) was used to characterize Rep protein structures.
  • Biophysical analyses were employed to study Rep oligomerization.
  • Structural determination of hexameric and dodecameric Rep states bound to ATPγS and ADP.

Main Results:

  • The hexameric structures of Redondovirus Rep bound to ATPγS and ADP were determined.
  • The ADP-bound Rep exhibited a staircase arrangement of DNA-binding loops, essential for SF3 helicase function.
  • 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 CRESS-DNA viruses.

Conclusions:

  • Structural insights into Redondovirus Rep provide a mechanistic understanding of CRESS-DNA virus replication.
  • The identified Rep oligomeric states and structural features offer new perspectives on viral DNA replication strategies.
  • This study lays the groundwork for understanding the broader functional roles of Rep proteins in CRESS-DNA viral systems.