A prominent β-hairpin structure in the winged-helix domain of RECQ1 is required for DNA unwinding and oligomer formation.
RecQ helicases have attracted considerable interest in recent years due to their role in the suppression of genome instability and human diseases. These atypical helicases exert their function by resolving a number of highly specific DNA structures. The crystal structure of a truncated catalytic core of the human RECQ1 helicase (RECQ1(49-616)) shows a prominent β-hairpin, with an aromatic residue (Y564) at the tip, located in the C-terminal winged-helix domain. Here, we show that the β-hairpin is required for the DNA unwinding and Holliday junction (HJ) resolution activity of full-length RECQ1, confirming that it represents an important determinant for the distinct substrate specificity of the five human RecQ helicases. In addition, we found that the β-hairpin is required for dimer formation in RECQ1(49-616) and tetramer formation in full-length RECQ1. We confirmed the presence of stable RECQ1(49-616) dimers in solution and demonstrated that dimer formation favours DNA unwinding; even though RECQ1 monomers are still active. Tetramers are instead necessary for more specialized activities such as HJ resolution and strand annealing. Interestingly, two independent protein-protein contacts are required for tetramer formation, one involves the β-hairpin and the other the N-terminus of RECQ1, suggesting a non-hierarchical mechanism of tetramer assembly.
International Centre for Genetic Engineering and Biotechnology, Padriciano 99, 34149 Trieste, Italy.
Bojana
B
Lucic
Ying
Y
Zhang
Oliver
O
King
Ramiro
R
Mendoza-Maldonado
Matteo
M
Berti
Frank H
FH
Niesen
Nicola A
NA
Burgess-Brown
Ashley C W
AC
Pike
Christopher D O
CD
Cooper
Opher
O
Gileadi
Alessandro
A
Vindigni
D004247:DNA / Q000378:metabolism*; D045566:DNA, Cruciform; D019281:Dimerization; D006801:Humans; D055503:Protein Multimerization; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D053484:RecQ Helicases / Q000737:chemistry* / Q000378:metabolism
D045566:DNA, Cruciform; D004247:DNA; C506725:RECQL protein, human; D053484:RecQ Helicases