Electron microscopic analysis of chromatin replication in the cellular blastoderm drosophila melanogaster embryo

McKnight, Steven L.; Miller, O. L.

doi:10.1016/0092-8674(77)90278-1

Cited by 228 publications

(143 citation statements)

References 23 publications

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“…Earlier studies of S phase 14 indicated that DNA replication begins immediately after mitosis 13, and that the bulk of replication occurs within the first 40 min of interphase, which lasts 70-170 min in different cells (Blumenthal et al, 1974;McKnight and Miller, 1977;. These studies, however, used methods that could not detect spatial differences in replication patterns, and thus would not have uncovered any differential regulation of S phases if it existed.…”

Section: Cell Cycle Progression Is Regulated In G2 During Embryonic Cmentioning

confidence: 99%

The three postblastoderm cell cycles of Drosophila embryogenesis are regulated in G2 by string

Edgar

O’Farrell

1990

Cell

421

326

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SummaryThe string (stg) locus of Drosophila encodes a factor that is thought to trigger mitosis by activating the p34 cdc2 protein kinase. stg is required for mitosis early in development and is transcribed in a dynamic pattern that anticipates the pattern of embryonic cell divisions. Here we show that differential cell cycle regulation during postblastoderm development (cell cycles 14-16) occurs in G2. We demonstrate that stg mRNA expressed from a heat shock promotor triggers mitosis, and an associated S phase, in G2 cells during these cycles. Hence, differential cell cycle timing at this developmental stage is controlled by stg. Finally, we use heat-induced stg expression to alter the normal pattern of embryonic mitoses. Surprisingly, the complex mitotic pattern evident during normal development is not essential for many features of pattern formation or for viability.

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Section: Cell Cycle Progression Is Regulated In G2 During Embryonic Cmentioning

confidence: 99%

The three postblastoderm cell cycles of Drosophila embryogenesis are regulated in G2 by string

Edgar

O’Farrell

1990

Cell

421

326

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“…Electron microscopy analysis of replicating DNA from Drosophila embryos suggested that origins fire synchronously at the syncitial blastoderm stage but become asynchronous at cellularization (MBT) (4,22). Different results were obtained when the replication of plasmid DNA or sperm nuclei in Xenopus egg extracts was examined.…”

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confidence: 99%

Aphidicolin Triggers a Block to Replication Origin Firing inXenopus Egg Extracts

Marheineke¹,

Hyrien

2001

Journal of Biological Chemistry

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DNA replication origins are located at random with respect to DNA sequence in Xenopus early embryos and on DNA replicated in Xenopus egg extracts. We have recently shown that origins fire throughout the S phase in Xenopus egg extracts. To study the temporal regulation of origin firing, we have analyzed origin activation in sperm nuclei treated with the DNA polymerase inhibitor aphidicolin. Sperm chromatin was incubated in Xenopus egg extracts in the presence of aphidicolin and transferred to a fresh extract, and digoxigenin-dUTP and biotin-dUTP were added at various times after aphidicolin release to selectively label early and late replicating DNA. Molecular combing analysis of single DNA fibers showed that only a fraction of potential origins were able to initiate in the presence of aphidicolin. After release from aphidicolin, the remaining origins fired asynchronously throughout the S phase. Therefore, initiation during the S phase depends on the normal progression of replication forks assembled at earlier activated origins. Caffeine, an inhibitor of the checkpoint kinases ATR and ATM, did not relieve the aphidicolin-induced block to origin firing. We conclude that a caffeine-insensitive intra-S phase checkpoint regulates origin activation when DNA synthesis is inhibited in Xenopus egg extracts.

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“…During chromatin assembly in S phase, there is random deposition of the preexisting as well as newly made histones onto the two daughter strands of DNA. In vivo, chromatin assembly appears to occur immediately following DNA replication (8,9); chromatin assembly can also take place in the absence of replication, presumably in response to nucleosome displacement or disassembly, thought to occur during transcription (10).…”

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confidence: 99%

Heterochromatin Protein 2 Interacts with Nap-1 and NURF: A Link between Heterochromatin-Induced Gene Silencing and the Chromatin Remodeling Machinery in Drosophila

et al. 2006

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Heterochromatin Protein 2 is a nonhistone chromosomal protein from Drosophila melanogaster that binds to HP1 and has been implicated in heterochromatin-induced gene silencing. Heretofore, HP1 has been the only known binding partner of HP2, a large protein devoid of sequence motifs other than a pair of AT-hooks. In an effort to identify proteins that interact with HP2 and assign functions to its various domains, nuclear proteins were fractionated under non-denaturing conditions. On separation of nuclear proteins, Nap-1, or Nucleosome assembly protein 1, has an overlapping elution profile with HP2 (assayed by Western blot) and has been identified by mass spectrometry in fractions with HP2. Upon probing fractions in which HP2 and Nap-1 are both present, we find that NURF, an ISWI-dependent chromatin remodeling complex, is also present. Results from coimmunoprecipitation experiments suggest that HP2 interacts with Nap-1 as well as with NURF; NURF appears to interact directly with both HP2 and Nap-1. Three distinct domains within HP2 mediate the interaction with NURF, allowing us to assign NURF binding domains in addition to the AT-hooks and HP1 binding domains already mapped in HP2. Mutations in Nap-1 are shown to suppress position effect variegation, suggesting that Nap-1 functions to help assemble chromatin into a closed form, as does HP2. Based on these interactions, we speculate that HP2 may cooperate with these factors in the remodeling of chromatin for silencing.Heterochromatin Protein 2 (HP2) was originally identified based on its ability to bind to Heterochromatin Protein 1 (HP1 1 ), one of the best-characterized nonhistone chromosomal proteins, in a yeast two-hybrid assay (1). HP2 colocalizes with HP1 at the pericentric heterochromatin of Drosophila polytene chromosomes, coimmunoprecipitates with HP1 from a Drosophila embryo extract, and is recruited to ectopic sites upon mislocalization of HP1. Analysis of the structure of the gene coding for HP2, Su(var)2-HP2, reveals two isoforms, a consequence of alternative splicing. Both proteins are large; the larger isoform of HP2 (HP2-L) is 356 kDa and the smaller isoform of HP2 (HP2-S) is 175 kDa. Both proteins are devoid of recognizable sequence motifs, except for two AT-hooks that are present only in the larger isoform. [AT-hooks are small, 9-aa DNA binding motifs which preferentially interact with ATCorrespondence to be sent to:

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Electron microscopic analysis of chromatin replication in the cellular blastoderm drosophila melanogaster embryo

Cited by 228 publications

References 23 publications

The three postblastoderm cell cycles of Drosophila embryogenesis are regulated in G2 by string

The three postblastoderm cell cycles of Drosophila embryogenesis are regulated in G2 by string

Aphidicolin Triggers a Block to Replication Origin Firing inXenopus Egg Extracts

Heterochromatin Protein 2 Interacts with Nap-1 and NURF: A Link between Heterochromatin-Induced Gene Silencing and the Chromatin Remodeling Machinery in Drosophila

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