Structural study of the function of Candida Albicans Pif1

Abstract

Pif1 helicases, conserved in eukaryotes, are involved in maintaining genome stability in both the nucleus and mitochondria. Here, we report the crystal structure of a truncated Candida Albicans Pif1 (CaPif1 ) in complex with ssDNA and an ATP analog. Our results show that the Q-motif is responsible for identifying adenine bases, and CaPif1 preferentially utilizes ATP/dATP during dsDNA unwinding. Although CaPif1 shares structural similarities with Saccharomyces cerevisiae Pif1, CaPif1 can contact the thymidine bases of DNA by hydrogen bonds, whereas ScPif1 cannot. More importantly, the crosslinking and mutant experiments have demonstrated that the conformational change of domain 2B is necessary for CaPifl1 to unwind dsDNA. These findings contribute to further the understanding of the unwinding mechanism of Pif1.

Structural mechanism underpinning Thermus oshimai Pif1‐mediated G‐quadruplex unfolding

“…Though Pif1 is conserved from bacteria to humans, Pif1 has very diverse functions in bacteria, yeast, and human. Pif1 sequence exhibits variations with the insertion domain 2C in budding yeast (Lu et al, 2018(Lu et al, , 2021 and accessory domains as WYL (Andis et al, 2018). Furthermore, sequence alignments show that some of the key residues identified in GRS are shared with other bacteria but not with Pif1 from eukaryotes (for an alignment, see fig S1 in Dai et al, 2021).…”

Structural Studies of Pif1 Helicases from Thermophilic Bacteria

“…and Thermus oshimai were solved in complex with different ligand, such as nucleotides and ssDNA [ 20 , 21 , 22 ], replication fork mimetic substrate [ 23 ], and G4 [ 24 ]. Human Pif1 exhibits a high structural conservation with bacterial Pif1 [ 21 , 25 ], but budding yeast Pif1 helicases are even longer and exhibit an inserted extra domain [ 26 , 27 ]. Little is known about the physiological functions of Pif1 in bacteria, although many hypotheses have been proposed [ 28 ].…”