title: XPB helicase regulates DNA incision by the Thermoplasma acidophilum endonuclease Bax1.
abstract: Bax1 has recently been identified as a novel binding partner for the archaeal helicase XPB. We previously characterized Bax1 from Thermoplasma acidophilum as a Mg²⁺-dependent structure-specific endonuclease. Here we directly compare the endonuclease activity of Bax1 alone or in combination with XPB. Using several biochemical and biophysical approaches, we demonstrate regulation of Bax1 endonuclease activity by XPB. Interestingly, incision assays with Bax1 and XPB/Bax1 clearly demonstrate that Bax1 produces different incision patterns depending on the presence or absence of XPB. Using atomic force microscopy (AFM), we directly visualize and compare binding of Bax1 and XPB/Bax1 to different DNA substrates. Our AFM data support enhanced DNA binding affinity of Bax1 in the presence of XPB. Taken together, the DNA incision and binding results suggest that XPB is able to load and position Bax1 on the scissile DNA substrate, thus increasing the DNA substrate range of Bax1.
authors.affiliation: Rudolf Virchow Center for Experimental Biomedicine, Würzburg, Germany.
authors.forename: Heide M
authors.initials: HM
authors.lastname: Roth
authors.forename: Johannes
authors.initials: J
authors.lastname: Römer
authors.forename: Verena
authors.initials: V
authors.lastname: Grundler
authors.forename: Bennett
authors.initials: B
authors.lastname: Van Houten
authors.forename: Caroline
authors.initials: C
authors.lastname: Kisker
authors.forename: Ingrid
authors.initials: I
authors.lastname: Tessmer
mesh_terms: D004249:DNA Damage; D004265:DNA Helicases / Q000378:metabolism*; D019641:DNA, Archaeal / Q000378:metabolism; D004270:DNA, Circular / Q000378:metabolism; D004720:Endonucleases / Q000378:metabolism*; D018625:Microscopy, Atomic Force; D011485:Protein Binding; D055503:Protein Multimerization; D013822:Thermoplasma / Q000201:enzymology*
chemical_list: D019641:DNA, Archaeal; D004270:DNA, Circular; D004720:Endonucleases; D004265:DNA Helicases