Inorganic pyrophosphatase is a component of the Drosophila nucleosome remodeling factor complex.
The Drosophila nucleosome remodeling factor (NURF) is a protein complex consisting of four polypeptides that facilitates the perturbation of chromatin structure in vitro in an ATP-dependent manner. The 140-kD NURF subunit, imitation switch (ISWI), is related to the SWI2/SNF2 ATPase. Another subunit, NURF-55, is a 55-kD WD repeat protein homologous to the human retinoblastoma-associated protein RbAp48. Here, we report the cloning and characterization of the smallest (38 kD) component of NURF. NURF-38 is strikingly homologous to known inorganic pyrophosphatases. Both recombinant NURF-38 alone and the purified NURF complex are shown to have inorganic pyrophosphatase activity. Inhibition of the pyrophosphatase activity of NURF with sodium fluoride has no significant effect on chromatin remodeling, indicating that these two activities may be biochemically uncoupled. Our results suggest that NURF-38 may serve a structural or regulatory role in the complex. Alternatively, because accumulation of unhydrolyzed pyrophosphate during nucleotide incorporation inhibits polymerization, NURF may also have been adapted to deliver pyrophosphatase to chromatin to assist in replication or transcription by efficient removal of the inhibitory metabolite.
Laboratory of Molecular Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-4255 USA.
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Gdula
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Sandaltzopoulos
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Tsukiyama
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Ossipow
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Wu
D000595:Amino Acid Sequence; D000818:Animals; D002843:Chromatin / Q000201:enzymology; D003001:Cloning, Molecular; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000201:enzymology* / Q000235:genetics; D004789:Enzyme Activation; D043564:Inorganic Pyrophosphatase; D019476:Insect Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009707:Nucleosomes / Q000201:enzymology* / Q000235:genetics; D011755:Pyrophosphatases / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013347:Subcellular Fractions / Q000201:enzymology
D002843:Chromatin; D029721:Drosophila Proteins; D019476:Insect Proteins; D046911:Macromolecular Substances; D009707:Nucleosomes; D011755:Pyrophosphatases; D043564:Inorganic Pyrophosphatase; C115568:Nurf-38 protein, Drosophila