Initiation of DNA replication requires the RECQL4 protein mutated in Rothmund-Thomson syndrome.
How the replication machinery is loaded at origins of DNA replication is poorly understood. Here, we implicate in this process the Xenopus laevis homolog (xRTS) of the RECQL4 helicase mutated in Rothmund-Thomson syndrome. xRTS, which bears homology to the yeast replication factors Sld2/DRC1, is essential for DNA replication in egg extracts. xRTS can be replaced in extracts by its human homolog, while RECQL4 depletion from mammalian cells induces proliferation failure, suggesting an evolutionarily conserved function. xRTS accumulates on chromatin during replication initiation, after prereplication-complex (pre-RC) proteins, Cut5, Sld5, or Cdc45 but before replicative polymerases. xRTS depletion suppresses the loading of RPA, the ssDNA binding protein that marks unwound origins before polymerase recruitment. However, xRTS is unaffected by xRPA depletion. Thus, xRTS functions after pre-RC formation to promote loading of replication factors at origins, a previously unrecognized activity necessary for initiation. This role connects defective replication initiation to a chromosome-fragility disorder.
Sangrithi
Mahesh N
MN
Cancer Research UK Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Hills Road, Cambridge CB2 2XZ, United Kingdom.
Bernal
Juan A
JA
Madine
Mark
M
Philpott
Anna
A
Lee
Joon
J
Dunphy
William G
WG
Venkitaraman
Ashok R
AR
D000251:Adenosine Triphosphatases / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D049109:Cell Proliferation; D003001:Cloning, Molecular; D004265:DNA Helicases / Q000235:genetics* / Q000378:metabolism; D004261:DNA Replication; D005816:Genetic Complementation Test; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D053484:RecQ Helicases; D011038:Rothmund-Thomson Syndrome / Q000201:enzymology* / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D029867:Xenopus Proteins / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis / Q000235:genetics*
D029867:Xenopus Proteins; D000251:Adenosine Triphosphatases; C506731:RECQL4 protein, human; D004265:DNA Helicases; D053484:RecQ Helicases; C502548:RTS protein, Xenopus