Nucleosome assembly: The CAF and the HAT

Current Opinion in Cell Biology

Volumn 8, Issue 3, 1996, Pages 369-373

  Kaufman, Paul D ^a,b  

^a Life Sciences Division   (United States)

^b UNIVERSITY OF CALIFORNIA   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

CHROMATIN ASSEMBLY FACTOR 1; HISTONE; HISTONE ACETYLTRANSFERASE; PROTEIN; UNCLASSIFIED DRUG;

ACETYLATION; CELL CYCLE S PHASE; DNA REPLICATION; GENE; MOLECULAR CLONING; NUCLEOSOME; PRIORITY JOURNAL; SHORT SURVEY;

EID: 0029938745     PISSN: 09550674     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0955-0674(96)80012-3     Document Type: Article

References (41)

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14. ••], will be important for eventually understanding how CAF-I specifically selects newly synthesized histones for deposition onto newly replicated DNA.
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17. ••]. This paper shows that a similar activity can be detected in crude fractions derived from Xenopus, and partial purification of a similar factor from Drosophila is also described. In addition, a new characteristic of both the recombinant human CAF-I and the Drosophila fraction is shown. When DNA replication reactions are incubated for an hour and the polymerases involved in DNA replication are then inhibited by the addition of aphidicolin, subsequent addition of CAF-I results in nucleosome assembly. This reaction is still linked to the process of DNA replication, however, because addition of aphidicolin before replication prevents the subsequent activity of CAF. It therefore appears that the DNA replication reaction changes the DNA template in such a way as to allow 'recognition' of the template by CAF, even if DNA polymerases are not simultaneously synthesizing nascent strands. This property of the activated template is labile. In other words, further incubation of the replicated DNA before addition of CAF gradually diminishes the ability of CAF to assemble nucleosomes when added.
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31. ••]). However, this paper raises more questions than it answers, because neither the original mutation nor complete disruption of HAT1 causes any known phenotype other than the biochemical defect. Because hat1 mutant cells still have 60% of the wild-type level of histone H4 acetyltransferase activity, it is likely that there are multiple redundant pathways involved in histone acetylation.
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36. •], serves as an intriguing example of how genetic and cell biological analyses need to be used in the study of chromatin assembly. In a search for proteins that interact with the B-type cyclins that are important for progression through the M phase of the cell cycle, the authors isolated a previously described protein called NAP-I (see [19,34]) from extracts of both yeast and Xenopus. The authors provide biochemical, genetic and cell biological data to show that yeast NAP-I is required for the cyclin Clb2 to perform its full range of functions in coordinating the cell cycle. One unanswered question, therefore, is whether NAP-I has any role in chromatin assembly in vivo. Alternatively, its activity as a nucleosome-assembly protein could be a biochemical artefact owing to its ability to serve as an acidic polymer like RNA [32] or polyglutamic acid [33]. As genetic data suggest that the NAP1 gene is required for microtubule dynamics, and biochemical data show that NAP-I binds both to core histones [41] and to cyclin B, another possibility is that the NAP-I family of proteins is involved in coordinating interactions between chromosomes, microtubules, and cyclin B during mitosis.
37. •].
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