Mutational Dissection of Telomeric DNA Binding Requirements of G4 Resolvase 1 Shows that G4-Structure and Certain 3'-Tail Sequences Are Sufficient for Tight and Complete Binding.

Journal Article (Journal Article)

Ends of human chromosomes consist of the six nucleotide repeat d[pTTAGGG]n known as telomeric DNA, which protects chromosomes. We have previously shown that the DHX36 gene product, G4 Resolvase 1 (G4R1), binds parallel G-quadruplex (G4) DNA with an unusually tight apparent Kd. Recent work associates G4R1 with the telomerase holoenzyme, which may allow it to access telomeric G4-DNA. Here we show that G4R1 can tightly bind telomeric G4-DNA, and in the context of the telomeric sequence, we determine length, sequence, and structural requirements sufficient for tight G4R1 telomeric binding. Specifically, G4R1 binds telomeric DNA in the K+-induced "3+1" G4-topology with an apparent Kd = 10 ± 1.9 pM, a value similar as previously found for binding to unimolecular parallel G4-DNA. G4R1 binds to the Na+-induced "2+2" basket G4-structure formed by the same DNA sequence with an apparent Kd = 71 ± 2.2 pM. While the minimal G4-structure is not sufficient for G4R1 binding, a 5' G4-structure with a 3' unstructured tail containing a guanine flanked by adenine(s) is sufficient for maximal binding. Mutations directed to disrupt G4-structure similarly disrupt G4R1 binding; secondary mutations that restore G4-structure also restore G4R1 binding. We present a model showing that a replication fork disrupting a T-loop could create a 5' quadruplex with an opened 3'tail structure that is recognized by G4R1.

Full Text

Duke Authors

Cited Authors

  • Smaldino, PJ; Routh, ED; Kim, JH; Giri, B; Creacy, SD; Hantgan, RR; Akman, SA; Vaughn, JP

Published Date

  • 2015

Published In

Volume / Issue

  • 10 / 7

Start / End Page

  • e0132668 -

PubMed ID

  • 26172836

Pubmed Central ID

  • PMC4501837

Electronic International Standard Serial Number (EISSN)

  • 1932-6203

Digital Object Identifier (DOI)

  • 10.1371/journal.pone.0132668


  • eng

Conference Location

  • United States