Human Werner helicase interacting protein 1 (WRNIP1) functions as a novel modulator for DNA polymerase delta.
Human WRNIP1, a Werner DNA helicase interacting protein 1, was expressed in insect cells and E. coli. The purified protein behaved as a homo-oligomeric complex with a native molecular mass indicative of an octamer, and the complex copurified with an ATPase activity that was stimulated by double-stranded DNA ends. As suggested by genetic studies of budding yeast WRNIP1/Mgs1, the purified human WRNIP1 complex interacted physically with human DNA polymerase delta (pol delta), stimulating its DNA synthesis activity more than fivefold in the presence or absence of proliferating cell nuclear antigen. Analysis of reaction products demonstrated the stimulation to be partly due to an increased processivity of pol delta but more importantly to an increase in its initiation frequency. Addition of ATP to reactions partially suppressed stimulation by WRNIP1. Furthermore, a mutant WRNIP1 lacking ATPase activity could stimulate pol delta normally but was insensitive to suppression by ATP. These results indicate that WRNIP1 functions as a modulator for initiation or restart events during pol delta-mediated DNA synthesis and that its ATPase activity is utilized to sense DNA ends and to regulate the extent of stimulation.
Tsurimoto
Toshiki
T
Department of Biology, School of Sciences, Kyushu University, Fukuoka 812-8581, Japan. ttsurscb@mbox.nc.kyushu-u.ac.jp
Shinozaki
Ayako
A
Yano
Masaki
M
Seki
Masayuki
M
Enomoto
Takemi
T
D000074183:ATPases Associated with Diverse Cellular Activities; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis*; D004265:DNA Helicases / Q000378:metabolism; D004258:DNA Polymerase III / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D005090:Exodeoxyribonucleases; D006801:Humans; D046911:Macromolecular Substances; D011485:Protein Binding; D053484:RecQ Helicases; D000071657:Werner Syndrome Helicase
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D004247:DNA; D004258:DNA Polymerase III; D005090:Exodeoxyribonucleases; D000251:Adenosine Triphosphatases; C430237:WRNIP1 protein, human; D000074183:ATPases Associated with Diverse Cellular Activities; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase