Hip, an HP1-interacting protein, is a haplo- and triplo-suppressor of position effect variegation

Schwendemann, Alexander; Matkovic, Tanja; Linke, Christian; Klebes, Ansgar; Hofmann, Annemarie; Korge, Günter

doi:10.1073/pnas.0705595105

Cited by 11 publications

(33 citation statements)

References 34 publications

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“…This is one indication that the interaction of the CSDs with the PX-VXL-like region(s) may be more complex than that predicted based on the results of the structural study of mouse HP1 (54). Similarly, the binding of the Drosophila HP1 CSD to Hip (HP1-interacting protein) was reported to differ from that of the mouse consensus PXVXL motif (47). Structural studies of HP1s in other organisms might reveal interesting differences in the binding mechanics of HP1s from various organisms.…”

Section: Discussionmentioning

confidence: 77%

Direct Interaction between DNA Methyltransferase DIM-2 and HP1 Is Required for DNA Methylation in Neurospora crassa

Honda

Selker

2008

Molecular and Cellular Biology

120

139

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DNA methylation is involved in gene silencing and genomic stability in mammals, plants, and fungi. Genetics studies of Neurospora crassa have revealed that a DNA methyltransferase (DIM-2), a histone H3K9 methyltransferase (DIM-5), and heterochromatin protein 1 (HP1) are required for DNA methylation. We explored the interrelationships of these components of the methylation machinery. A yeast two-hybrid screen revealed that HP1 interacts with DIM-2. We confirmed the interaction in vivo and demonstrated that it involves a pair of PXVXL-related motifs in the N-terminal region of DIM-2 and the chromo shadow domain of HP1. Both regions are essential for proper DNA methylation. We also determined that DIM-2 and HP1 form a stable complex independently of the trimethylation of histone H3K9, although the association of DIM-2 with its substrate sequences depends on trimethyl-H3K9. The DIM-2/HP1 complex does not include DIM-5. We conclude that DNA methylation in Neurospora is largely or exclusively the result of a unidirectional pathway in which DIM-5 methylates histone H3K9 and then the DIM-2/HP1 complex recognizes the resulting trimethyl-H3K9 mark via the chromo domain of HP1.In most eukaryotic organisms, genomic DNA is modified by the enzymatic conversion of certain cytosines to 5-methylcytosines. DNA methylation directly and indirectly influences gene expression and plays crucial roles in fundamental biological processes, such as X chromosome inactivation, genomic imprinting, and silencing of selfish DNA (5,17,21,25,29,44). DNA methylation is also thought to play key roles in tumorigenesis; inappropriate methylation can silence tumor-suppressor genes and/or activate oncogenes (14). Aberrant DNA methylation is associated with other diseases, most notably immunodeficiency, centromere instability, and facial anomalies syndrome in humans (2). Although information on the relationship between DNA methylation and human diseases is accumulating, basic questions, such as how DNA methylation is controlled and how it functions, remain unanswered.The results of research on DNA methylation using the filamentous fungus Neurospora crassa revealed that DNA methylation is controlled by the state of underlying chromatin proteins (17). In eukaryotic cells, DNA is wrapped around a protein octamer composed of histones (H2A, H2B, H3, and H4), which are subject to a variety of posttranslational modifications, including methylation, acetylation, phosphorylation, and ubiquitylation (3). The results of genetic studies in Neurospora demonstrated that condensed chromatin ("heterochromatin") associated with methylated lysine 9 of histone H3 (H3K9) is involved in DNA methylation. Mutations in either dim-5 or hpo, which, respectively, encode the DIM-5/KMT1 histone methyltransferase (HMTase) and heterochromatin protein 1 (HP1), eliminate all detectable DNA methylation, just like null mutations in the DNA methyltransferase (DMTase) gene dim-2 (16, 30, 51). The DIM-5 HMTase specifically trimethylates H3K9, and trimethyl-H3K9 (H3K9me3) is preferentially ...

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Section: Discussionmentioning

confidence: 77%

Direct Interaction between DNA Methyltransferase DIM-2 and HP1 Is Required for DNA Methylation in Neurospora crassa

Honda

Selker

2008

Molecular and Cellular Biology

120

139

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“…To determine whether tethered HP1 is able to maintain these interactions at sites of ectopic heterochromatin, colocalization studies on polytene chromosomes were performed. HP1-interacting protein (Hip), shows colocalization with HP1 in heterochromatic regions of polytene chromosomes and requires HP1 for chromosome association (Schwendemann et al 2008). Immunofluorescence microscopy of polytene chromosomes showed that LacI-HP1 recruited Hip to sites of ectopic heterochromatin ( Figure 2).…”

Section: Resultsmentioning

confidence: 99%

“…05-501, clone 9A5, 1:300 dilution), followed by goat anti-mouse FITC ( Jackson Immunoresearch Laboratories, 1:200) or Alexa Fluor 546 donkey anti-mouse (Invitrogen, 1:200) after a 1-hr heat shock treatment according to published procedures (Li et al 2003). Hip was detected using previously described rabbit antibodies to Hip (Schwendemann et al 2008;1:50) followed by Alexa Fluor 488 goat anti-rabbit (Invitrogen, 1:300). dSETDB1 detection was carried out using previously described rat antibodies (Clough et al 2007;1:150) followed by donkey anti-rat FITC ( Jackson Immunoresearch Laboratories, 1:200).…”

Section: Methodsmentioning

confidence: 99%

“…Taken together, these data suggest that full-length HP1 is needed for proper association at the chromocenter. Tethered HP1 recruits Hip and Suv4-20: HP1 has numerous interaction partners, some of which colocalize with HP1 at heterochromatin (Pak et al 1997;Schotta et al 2002;Schwendemann et al 2008). To determine whether tethered HP1 is able to maintain these interactions at sites of ectopic heterochromatin, colocalization studies on polytene chromosomes were performed.…”

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Domains of Heterochromatin Protein 1 Required forDrosophila melanogasterHeterochromatin Spreading

et al. 2009

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Centric regions of eukaryotic genomes are packaged into heterochromatin, which possesses the ability to spread along the chromosome and silence gene expression. The process of spreading has been challenging to study at the molecular level due to repetitious sequences within centric regions. A heterochromatin protein 1 (HP1) tethering system was developed that generates ''ectopic heterochromatin'' at sites within euchromatic regions of the Drosophila melanogaster genome. Using this system, we show that HP1 dimerization and the PxVxL interaction platform formed by dimerization of the HP1 chromo shadow domain are necessary for spreading to a downstream reporter gene located 3.7 kb away. Surprisingly, either the HP1 chromo domain or the chromo shadow domain alone is sufficient for spreading and silencing at a downstream reporter gene located 1.9 kb away. Spreading is dependent on at least two H3K9 methyltransferases, with SU(VAR)3-9 playing a greater role at the 3.7-kb reporter and dSETDB1 predominately acting at the 1.9 kb reporter. These data support a model whereby HP1 takes part in multiple mechanisms of silencing and spreading.H ETEROCHROMATIN protein 1 (HP1) was identified in Drosophila as a nonhistone chromosomal protein enriched in centric heterochromatin ( James and Elgin 1986;James et al. 1989). On polytene chromosomes, HP1 localizes near centromeres and telomeres, along the fourth chromosome and at $200 sites within the euchromatic arms ( James et al. 1989;Fanti et al. 2003). Heterochromatin has the ability to ''spread,'' or propagate in cis, along the chromosome (Weiler and Wakimoto 1995). Spreading is observed when a chromosomal rearrangement places a euchromatic domain next to a heterochromatic domain. Cytologically, spreading is visualized as densely compact chromatin that emanates from the chromocenter, the structure formed by the fusion of centromeres, and extends into the banded regions of polytene chromosomes (Belyaeva and Zhimulev 1991). Euchromatic genes brought into juxtaposition with heterochromatin by chromosomal rearrangements exhibit gene silencing, termed position effect variegation (PEV) (Weiler and Wakimoto 1995). Mutations in Su(var)2-5, the gene encoding HP1, suppress silencing, suggesting HP1 plays a key role in spreading (Eissenberg et al. 1990). The molecular processes of spreading are not well understood.Repetitive sequences within heterochromatin make it difficult to study spreading at the molecular level. In addition, specific repetitive elements are thought to function as initiation sites for heterochromatin formation (Sun et al. 2004;Haynes et al. 2006), making it challenging to separate initiation from spreading. To overcome these problems, we generated a system that nucleates small domains (,20 kb) of repressive chromatin that share many properties with centric heterochromatin. Here we refer to these as ectopic heterochromatin domains. These domains are generated by expressing a fusion protein, consisting of the DNA binding domain of the Escherichia coli lac represso...

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“…The number of identified factors that influence chromatin quality is continuously increasing. Protein interaction screens reveal more and more new components involved in the regulation of gene expression and structuring of chromatin (Giot et al 2003;Schwendemann et al 2008). In order to improve our knowledge about chromatin structure and function, it is very important to identify as many components as possible.…”

Section: Introductionmentioning

confidence: 99%

The winged-helix transcription factor JUMU is a haplo-suppressor/triplo-enhancer of PEV in various tissues but exhibits reverse PEV effects in the brain of Drosophila melanogaster

2009

Self Cite

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Gene expression goes along with changes in chromatin structure and is regulated by chromatin-modifying factors. If genes are transposed from their euchromatic position to the vicinity of heterochromatin, their expression can underly a position effect variegation (PEV). In Drosophila melanogaster a few genes are known that function in a gene dose-dependent manner as haplo-suppressors and triplo-enhancers of PEV or vice versa. The gene jumeaux (jumu) encodes a winged-helix transcription factor of multiple regulatory functions. A novel PEV test system for Drosophila melanogaster reveals that JUMU behaves as a haplo-suppressor/triplo-enhancer in different larval and adult tissues, but surprisingly behaves in the reverse manner as a haplo-enhancer/triplo-suppressor in larval and adult brains. Like jumu, the Su(var)3-9 gene also behaves as a haplo-suppressor/triplo-enhancer, but in our test system does not show any PEV effect in the brains.

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Hip, an HP1-interacting protein, is a haplo- and triplo-suppressor of position effect variegation

Cited by 11 publications

References 34 publications

Direct Interaction between DNA Methyltransferase DIM-2 and HP1 Is Required for DNA Methylation in Neurospora crassa

Direct Interaction between DNA Methyltransferase DIM-2 and HP1 Is Required for DNA Methylation in Neurospora crassa

Domains of Heterochromatin Protein 1 Required forDrosophila melanogasterHeterochromatin Spreading

The winged-helix transcription factor JUMU is a haplo-suppressor/triplo-enhancer of PEV in various tissues but exhibits reverse PEV effects in the brain of Drosophila melanogaster

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