Replication focus-forming activity 1 and the Werner syndrome gene product.
The initiation of DNA replication involves a minimum of four factors: a specific DNA sequence (origin), an initiator protein which binds to the origin, a helicase that unwinds the origin and a protein that binds single-stranded DNA that stabilizes the unwound origin. In eukaryotic cells, the origin recognition complex (ORC) is the initiator protein and replication protein A (RPA; ref. 3) is the single-stranded DNA-binding protein. However, the helicase has not been identified and the nature of origins remains elusive, except in the case of Saccharomyces cerevisiae. A unique feature of eukaryotic DNA replication is that it occurs at a few-hundred discrete foci. It has thus been proposed that a real origin must contain a specific DNA sequence and must be attached to replication foci. Using Xenopus laevis egg extracts, we have identified and purified a 170-kD protein, focus-forming activity 1 (FFA-1), which is required for the formation of replication foci. Here we report that FFA-1 has DNA-helicase activity. Moreover, it is a homologue of the human Werner syndrome gene product WRN, a protein associated with premature ageing in humans.
Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA. hong_yan@fccc.edu
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D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D004261:DNA Replication / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005090:Exodeoxyribonucleases; D006801:Humans; D008969:Molecular Sequence Data; D053484:RecQ Helicases; D051716:Replication Protein A; D017386:Sequence Homology, Amino Acid; D014898:Werner Syndrome / Q000235:genetics; D000071657:Werner Syndrome Helicase; D014982:Xenopus laevis
D004268:DNA-Binding Proteins; C497167:RPA1 protein, human; D051716:Replication Protein A; D000255:Adenosine Triphosphate; D004247:DNA; D005090:Exodeoxyribonucleases; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase