InterPro domain: IPR010285

This entry includes a group of DNA helicases, including Pif1 and Rrm3 from budding yeasts and Pfh1 from fusion yeast. This entry also includes Pif1 like proteins from prokaryotes and eukaryotes including plants.

Pif1 is a DNA helicase conserved from bacteria to humans [ 1 , 2 ]. It suppresses both G-quadruplex-associated DNA damage and telomere lengthening. In budding yeast, it exists in two forms, nuclear form and mitochondrial form. Its nuclear form inhibits telomerase, while its mitochondrial form is involved in repair and recombination of mitochondrial DNA [ 3 , 4 ].

In budding yeasts, another DNA replicative helicase, Rrm3 is recruited to paused replisomes to promote fork progression throughout nonhistone protein-DNA complexes, naturally occurring impediments that are encountered in each S phase where replication forks pauses [ 5 ]. It shares protein sequence similarities with another DNA helicase, Pif1. However, their functions are different. Rrm3 promotes telomere replication, while Pif1 inhibits telomere replication [ 5 ]. They also have opposite effects on replication fork progression in ribosomal DNA [ 5 ].

In fission yeasts, Pfh1 is required for the maintenance of both mitochondrial and nuclear genome stability [ 5 , 6 ].

1. Human PIF helicase is cell cycle regulated and associates with telomerase. Cell Cycle 5, 2796-804
2. The human Pif1 helicase, a potential Escherichia coli RecD homologue, inhibits telomerase activity. Nucleic Acids Res. 34, 1393-404
3. Pif1p helicase, a catalytic inhibitor of telomerase in yeast. Science 289, 771-4
4. The Saccharomyces Pif1p DNA helicase and the highly related Rrm3p have opposite effects on replication fork progression in ribosomal DNA. Cell 100, 479-89
5. Schizosaccharomyces pombe pfh1+ encodes an essential 5' to 3' DNA helicase that is a member of the PIF1 subfamily of DNA helicases. Mol. Biol. Cell 13, 2180-91
6. The Schizosaccharomyces pombe Pfh1p DNA helicase is essential for the maintenance of nuclear and mitochondrial DNA. Mol. Cell. Biol. 28, 6594-608