Expression of ISWI and its binding to chromatin during the cell cycle and early development.
We have characterized Xenopus ISWI, a catalytic subunit of a family of chromatin-remodeling complexes. We show that ISWI is expressed constitutively during development but poorly expressed in adult tissues except oocytes which contain a large store of maternal protein. We further analyzed its localization both in vivo and in vitro in Xenopus cell cycle extracts and identified that ISWI binds to chromatin at the G1-S period. However, its association to chromatin does not require ongoing DNA replication. Immunodepletion of ISWI has no effect on either sperm chromatin decondensation or the kinetics and efficiency of DNA replication. Nucleosome assembly also occurs in ISWI-depleted extracts, but nucleosome spacing is disturbed. From these results, we conclude that ISWI is not necessary for sperm chromatin decondensation and the accelerated rates of DNA replication that characterize early development.
Demeret
Caroline
C
Institute of Human Genetics, CNRS, Genome Dynamics and Development, 141, rue de la Cardonille, 34396 5, Montpellier Cedex, France.
Bocquet
Stéphane
S
Lemaítre
Jean Marc
JM
Françon
Patricia
P
Méchali
Marcel
M
D000251:Adenosine Triphosphatases / Q000096:biosynthesis* / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D002453:Cell Cycle; D002499:Centrifugation, Density Gradient; D002843:Chromatin / Q000378:metabolism*; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000378:metabolism; D016193:G1 Phase; D015151:Immunoblotting; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009707:Nucleosomes / Q000378:metabolism; D011485:Protein Binding; D016196:S Phase; D017386:Sequence Homology, Amino Acid; D013395:Sucrose / Q000494:pharmacology; D013997:Time Factors; D014018:Tissue Distribution; D014157:Transcription Factors / Q000096:biosynthesis* / Q000737:chemistry*; D014981:Xenopus
D002843:Chromatin; D018076:DNA, Complementary; C086468:ISWI protein; D009707:Nucleosomes; D014157:Transcription Factors; D013395:Sucrose; D000251:Adenosine Triphosphatases