title: DNA synthesis provides the driving force to accelerate DNA unwinding by a helicase.
abstract: Helicases are molecular motors that use the energy of nucleoside 5'-triphosphate (NTP) hydrolysis to translocate along a nucleic acid strand and catalyse reactions such as DNA unwinding. The ring-shaped helicase of bacteriophage T7 translocates along single-stranded (ss)DNA at a speed of 130 bases per second; however, T7 helicase slows down nearly tenfold when unwinding the strands of duplex DNA. Here, we report that T7 DNA polymerase, which is unable to catalyse strand displacement DNA synthesis by itself, can increase the unwinding rate to 114 base pairs per second, bringing the helicase up to similar speeds compared to its translocation along ssDNA. The helicase rate of stimulation depends upon the DNA synthesis rate and does not rely on specific interactions between T7 DNA polymerase and the carboxy-terminal residues of T7 helicase. Efficient duplex DNA synthesis is achieved only by the combined action of the helicase and polymerase. The strand displacement DNA synthesis by the DNA polymerase depends on the unwinding activity of the helicase, which provides ssDNA template. The rapid trapping of the ssDNA bases by the DNA synthesis activity of the polymerase in turn drives the helicase to move forward through duplex DNA at speeds similar to those observed along ssDNA.
authors.affiliation: Department of Biochemistry, UMDNJ-Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, New Jersey 08854, USA.
authors.forename: Natalie M
authors.initials: NM
authors.lastname: Stano
authors.forename: Yong-Joo
authors.initials: YJ
authors.lastname: Jeong
authors.forename: Ilker
authors.initials: I
authors.lastname: Donmez
authors.forename: Padmaja
authors.initials: P
authors.lastname: Tummalapalli
authors.forename: Mikhail K
authors.initials: MK
authors.lastname: Levin
authors.forename: Smita S
authors.initials: SS
authors.lastname: Patel
mesh_terms: D017122:Bacteriophage T4 / Q000201:enzymology; D017123:Bacteriophage T7 / Q000201:enzymology; D020029:Base Pairing; D001483:Base Sequence; D004247:DNA / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D019915:DNA Primase / Q000378:metabolism*; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D007700:Kinetics; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D014764:Viral Proteins; C069983:gene 43 protein, Enterobacteria phage T4; D004247:DNA; D019915:DNA Primase; C034970:bacteriophage T7 induced DNA polymerase; D004259:DNA-Directed DNA Polymerase