DNA helicase (5’-3’) that  may help  to promote replisome progression in some regions of the genome such as the rRNA genes. Related to Rrm3.





Molecular weight

98 kDa

Biochemical properties

DNA helicase prefers to unwind RNA:DNA hybrids than DNA:DNA (1)



Protein interactions


•Cac1 (2)

•recQ (sgs1) suppresses (3)



•Telomerase (4)






Cellular location and expression


Other comments


• Suggested role in rDNA replication –less recombination (popped out circles) if lost (5) opposing effect to rrm3

• role in telomere maintenance and (2) reduces processivity of telomerase (6)

•Suggested role with DNA2 in okazaki fragment synthesis (7)



 • Essential, post initiation defect in DNA replication? Suggest some role in replication (8)


Revised by


Last edited

15 April 08



1.    Boule,J.B. and Zakian,V.A. (2007) The yeast Pif1p DNA helicase preferentially unwinds RNA DNA substrates. Nucleic Acids Res 35, 5809-5818.

2.    Bessler,J.B., Torredagger,J.Z. and Zakian,V.A. (2001) The Pif1p subfamily of helicases: region-specific DNA helicases? Trends Cell Biol 11, 60-65.

3.    Wagner,M., Price,G. and Rothstein,R. (2006) The absence of Top3 reveals an interaction between the Sgs1 and Pif1 DNA helicases in Saccharomyces cerevisiae. Genetics 174, 555-573.

4.    Mateyak,M.K. and Zakian,V.A. (2006) Human PIF helicase is cell cycle regulated and associates with telomerase. Cell Cycle 5, 2796-2804.

5.    Ivessa,A.S., Zhou,J.Q. and Zakian,V.A. (2000) The Saccharomyces Pif1p DNA helicase and the highly related Rrm3p have opposite effects on replication fork progression in ribosomal DNA. Cell 100, 479-489.

6.    Boule,J.B., Vega,L.R. and Zakian,V.A. (2005) The yeast Pif1p helicase removes telomerase from telomeric DNA. Nature 438, 57-61.

7.    Budd,M.E., Reis,C.C., Smith,S., Myung,K. and Campbell,J.L. (2006) Evidence suggesting that Pif1 helicase functions in DNA replication with the Dna2 helicase/nuclease and DNA polymerase delta. Mol Cell Biol 26, 2490-2500.

8.    Zhou,J.Q., Qi,H., Schulz,V.P., Mateyak,M.K., Monson,E.K. and Zakian,V.A. (2002) Schizosaccharomyces pombe pfh1+ encodes an essential 5' to 3' DNA helicase that is a member of the PIF1 subfamily of DNA helicases. Mol Biol Cell13, 2180-2191.