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

Stephens, Gena E.; Xiao, Hua; Lankenau, Dirk-H.; Wu, Carl; Elgin, Sarah C. R.

doi:10.1021/bi060983y

Cited by 17 publications

(13 citation statements)

References 41 publications

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“…Notably, an intrinsic transcriptional repression function was observed when NAP1 was tethered to DNA. In line with this observation, very recently findings revealed that NAP1 is associated with the heterochromatic protein 2, HP2, in Drosophila, suggesting that NAP1 is in part associated with heterochromatin (35). Whether this is a direct cause through nucleosome deposition or is mediated by other interacting proteins has to be investigated.…”

Section: Discussionmentioning

confidence: 83%

The Nucleosome Assembly Activity of NAP1 Is Enhanced by Alien

Eckey

Wang

Papaioannou

et al. 2007

Molecular and Cellular Biology

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The assembly of nucleosomes into chromatin is essential for the compaction of DNA and inactivation of the DNA template to modulate and repress gene expression. The nucleosome assembly protein 1, NAP1, assembles nucleosomes independent of DNA synthesis and was shown to enhance coactivator-mediated gene expression, suggesting a role for NAP1 in transcriptional regulation. Here, we show that Alien, known to harbor characteristics of a corepressor of nuclear hormone receptors such as of the vitamin D receptor (VDR), binds in vivo and in vitro to NAP1 and modulates its activity by enhancing NAP1-mediated nucleosome assembly on DNA. Furthermore, Alien reduces the accessibility of the histones H3 and H4 for NAP1-promoted assembly reaction. This indicates that Alien sustains and reinforces the formation of nucleosomes. Employing deletion mutants of Alien suggests that different regions of Alien are involved in enhancement of NAP1-mediated nucleosome assembly and in inhibiting the accessibility of the histones H3 and H4. In addition, we provide evidence that Alien is associated with chromatin and with micrococcus nuclease-prepared nucleosome fractions and interacts with the histones H3 and H4. Furthermore, chromatin immunoprecipitation and reimmunoprecipitation experiments suggest that NAP1 and Alien localize to the endogenous CYP24 promoter in vivo, a VDR target gene. Based on these findings, we present here a novel pathway linking corepressor function with nucleosome assembly activity.

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Section: Discussionmentioning

confidence: 83%

The Nucleosome Assembly Activity of NAP1 Is Enhanced by Alien

Eckey

Wang

Papaioannou

et al. 2007

Molecular and Cellular Biology

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“…The Nap1-null mutant allele is homozygous-lethal (Stephens et al 2006), whereas Nlp/Nph and P32 are not. To better understand interactions among protamine chaperones in vivo, we combined Nlp/Nph and P32 mutations and discovered significant recessive and dominant interactions (Table 2).…”

Section: Histone Chaperone Activity Of Tap/p32mentioning

confidence: 99%

Drosophila TAP/p32 is a core histone chaperone that cooperates with NAP-1, NLP, and nucleophosmin in sperm chromatin remodeling during fertilization

et al. 2014

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Nuclear DNA in the male gamete of sexually reproducing animals is organized as sperm chromatin compacted primarily by sperm-specific protamines. Fertilization leads to sperm chromatin remodeling, during which protamines are expelled and replaced by histones. Despite our increased understanding of the factors that mediate nucleosome assembly in the nascent male pronucleus, the machinery for protamine removal remains largely unknown. Here we identify four Drosophila protamine chaperones that mediate the dissociation of protamine-DNA complexes: NAP-1, NLP, and nucleophosmin are previously characterized histone chaperones, and TAP/p32 has no known function in chromatin metabolism. We show that TAP/p32 is required for the removal of Drosophila protamine B in vitro, whereas NAP-1, NLP, and Nph share roles in the removal of protamine A. Embryos from P32-null females show defective formation of the male pronucleus in vivo. TAP/p32, similar to NAP-1, NLP, and Nph, facilitates nucleosome assembly in vitro and is therefore a histone chaperone. Furthermore, mutants of P32, Nlp, and Nph exhibit synthetic-lethal genetic interactions. In summary, we identified factors mediating protamine removal from DNA and reconstituted in a defined system the process of sperm chromatin remodeling that exchanges protamines for histones to form the nucleosome-based chromatin characteristic of somatic cells.

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“…ACF has also been shown to bind directly to the Drosophila HP-1 variant dHP-1a, and aid its loading to chromatin [14]. A recent report shows a physical interaction of the NuRF complex with the heterochromatin protein dHP-2, although the NURF301 subunit failed to show any genetic effect on heterochromatin formation [15]. Finally, purification of a complex containing the methyltransferase Clr3 from Schizosaccharomyces pombe revealed the presence of the Mit1 protein, whose chromatin remodelling activity was necessary for heterochromatin formation [16].…”

Section: Introductionmentioning

confidence: 99%

The Chromatin Remodelling Factor dATRX Is Involved in Heterochromatin Formation

et al. 2008

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Despite extensive study of heterochromatin, relatively little is known about the mechanisms by which such a structure forms. We show that the Drosophila homologue of the human α-thalassemia and mental retardation X-linked protein (dATRX), is important in the formation or maintenance of heterochromatin through modification of position effect variegation. We further show that there are two isoforms of the dATRX protein, the longer of which interacts directly with heterochromatin protein 1 (dHP-1) through a CxVxL motif both in vitro and in vivo. These two proteins co-localise at heterochromatin in a manner dependent on this motif. Consistent with this observation, the long isoform of the dATRX protein localises primarily to the heterochromatin at the chromocentre on salivary gland polytene chromosomes, whereas the short isoform binds to many sites along the chromosome arms. We suggest that the establishment of a regular nucleosomal organisation may be common to heterochromatin and transcriptionally repressed chromatin in other locations, and may require the action of ATP dependent chromatin remodelling factors.

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

Cited by 17 publications

References 41 publications

The Nucleosome Assembly Activity of NAP1 Is Enhanced by Alien

The Nucleosome Assembly Activity of NAP1 Is Enhanced by Alien

Drosophila TAP/p32 is a core histone chaperone that cooperates with NAP-1, NLP, and nucleophosmin in sperm chromatin remodeling during fertilization

The Chromatin Remodelling Factor dATRX Is Involved in Heterochromatin Formation

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