Heterochromatin protein 2 (HP2), a partner of HP1 in
            <i>Drosophila</i>
            heterochromatin

The structural and functional analyses of heterochromatin are essential to understanding how heterochromatic genes are regulated and how centromeric chromatin is formed. Because the repetitive nature of heterochromatin hampers its genome analysis, new approaches need to be developed. Here, we describe how, in double mutants for Su(var)3-9 and SuUR genes encoding two structural proteins of heterochromatin, new banded heterochromatic segments appear in all polytene chromosomes due to the strong suppression of under-replication in pericentric regions. FISH on salivary gland polytene chromosomes from these double mutant larvae allows high resolution of heterochromatin mapping. In addition, immunostaining experiments with a set of antibodies against euchromatic and heterochromatic proteins reveal their unusual combinations in the newly appeared segments: binding patterns for HP1 and HP2 are coincident, but both are distinct from H3diMetK9 and H4triMetK20. In several regions, partial overlapping staining is observed for the proteins characteristic of active chromatin RNA Pol II, H3triMetK4, Z4, and JIL1, the boundary protein BEAF, and the heterochromatin-enriched proteins HP1, HP2, and SU(VAR)3-7. The exact cytological position of the centromere of chromosome 3 was visualized on salivary gland polytene chromosomes by using the centromeric dodeca satellite and the centromeric protein CID. This region is enriched in H3diMetK9 and H4triMetK20 but is devoid of other proteins analyzed.Drosophila melanogaster ͉ genome analysis

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“…We also found that HP1 and HP2 colocalized (Fig. 3J) as previously described (49). H3diMetK9 was found at rare sites within PA (Fig.…”

Section: Immunocytological Analysis Of Chromosomal Proteins Within Thesupporting

confidence: 88%

High-resolution analysis of Drosophila heterochromatin organization using SuUR Su(var)3-9 double mutants

Andreyeva

Колесникова

Demakova

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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“…We have localized SU(VAR)3-7 [detected in telomeric regions and pericentric heterochromatin (Delattre et al, 2000)] and HP2 [the HP1 partner (Shaffer et al, 2002)] to the very tips of Tel/+ chromosomes, in addition to HP1 (Siriaco et al, 2002) and SUUR (Fig. 1C, Fig.…”

Section: Resultsmentioning

confidence: 89%

“…These are HP2 (Shaffer et al, 2002), SU(VAR)3-7 (Delattre et al, 2000), SUUR (Makunin et al, 2002) and H3Me3K27 (Perrini et al, 2004;Ebert et al, 2004) ( Table 3). Association of HP1 and HOAP with the cap region has been demonstrated (Fanti et al, 1998;Siriaco et al, 2002;Cenci et al, 2003).…”

Section: Discussionmentioning

confidence: 99%

Three distinct chromatin domains in telomere ends of polytene chromosomes inDrosophila melanogaster Telmutants

Andreyeva

Belyaeva

Semeshin

et al. 2005

Journal of Cell Science

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IntroductionTelomeres are specialized DNA-protein complexes that cap the termini of linear chromosomes. They compensate for incomplete DNA replication and contribute to the stability of chromosomes and karyotype (Muller, 1932;Pardue and Debaryshe, 1999;Biessmann and Mason, 2003). Telomeres also participate in nuclear architecture maintenance, and are known to associate with nuclear lamina (Hochstrasser et al., 1986;Marshall et al., 1996;Hari et al., 2001) or with nuclear matrix (de Lange, 1992;Luderus et al., 1996). However, the factors that underlie these phenomena, as well as the mechanisms of telomere functioning, remain poorly understood in Drosophila melanogaster.In eukaryotes, such as budding yeast, fission yeast and humans, telomeres are considered to be essentially heterochromatic (Perrod and Gasser, 2003). Heterochromatin is characterized by a high degree of DNA compaction, late replication in S phase, and by association with specific silencing proteins (Richards and Elgin, 2002). Intercalary (IH) and pericentric heterochromatin regions in many Diptera species are characterized by DNA underreplication and nonhomologous (ectopic) pairing of chromosomal regions in polytene chromosomes (Zhimulev, 1998). The question whether D. melanogaster telomeres are heterochromatic in

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“…NURF has been shown to bind to factors that are involved in active transcription, such as GAGA factor and HSF (25). However, the same chromatin remodeling complex might well function to move nucleosomes into a more regular ordered array when bound to factors such as HP2, which contributes to initiation and/or spreading of heterochromatin in PEV (1). Recent data indeed indicates this.…”

Section: Discussionmentioning

confidence: 99%

“…Mutations in Su(var)2-HP2 act as dominant suppressors of position effect variegation (PEV) monitored by w m4 , a chromosome rearrangement (1). PEV occurs when a gene that is normally found in a euchromatic region is transposed to a position within or in close proximity to heterochromatin; a variegating phenotype results as the gene is silenced in some of the cells in which it is normally expressed (4).…”

mentioning

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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Heterochromatin protein 2 (HP2), a partner of HP1 in Drosophila heterochromatin

Cited by 46 publications

References 47 publications

High-resolution analysis of Drosophila heterochromatin organization using SuUR Su(var)3-9 double mutants

High-resolution analysis of Drosophila heterochromatin organization using SuUR Su(var)3-9 double mutants

Three distinct chromatin domains in telomere ends of polytene chromosomes inDrosophila melanogaster Telmutants

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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