- Tools
- Downloads
- Links
- Community
- About
- Help
FB2026_01
,
released March 12, 2026
HP1, HP1a, Su(var)2-5, heterochromatin protein 1, HP-1
chromodomain - Polycomb group - chromatin associated protein - required both for activation of heterochromatic genes and silencing of euchromatic genes
Please see the JBrowse view of Dmel\Su(var)205 for information on other features
To submit a correction to a gene model please use the Contact FlyBase form
AlphaFold produces a per-residue confidence score (pLDDT) between 0 and 100. Some regions with low pLDDT may be unstructured in isolation.
Low-frequency RNA-Seq exon junction(s) not annotated.
Gene model reviewed during 5.45
The group(s) of polypeptides indicated below share identical sequence to each other.
206 (aa)
Homodimer (PubMed:17875665). Probably associates with Su(var)3-9 (PubMed:17875665). Interacts with Mcm10 (PubMed:12808023). Interacts (via chromoshadow domain) with piwi (via N-terminal region) (PubMed:17875665). Interacts with Rrp6 (PubMed:26389589). Associates with and may be part of the HipHop-HOAP telomere capping complex but is not required for its stability or telomere localization (PubMed:20057353). Interacts (via the chromo domain 2 (chromoshadow domain) and the hinge region between chromo domains 1 and 2) with cav/HOAP (via C-terminus); the interaction is direct (PubMed:11408576, PubMed:12826664, PubMed:19181850). Each molecule of cav/HOAP interacts with 2 molecules of Su(var)205/HP1 (PubMed:12826664). Interacts with HipHop (via N-terminus) (PubMed:20057353). Interacts with moi/modigliani; the interaction is direct (PubMed:19181850). Interacts (via chromo domain 1) with His3/histone 3 (via N-terminal tail methylated at 'Lys-10'); the interaction is direct (PubMed:11859155).
Click to get a list of regulatory features (enhancers, TFBS, etc.) and gene disruptions (point mutations, indels, etc.) within or overlapping Dmel\Su(var)205 using the Feature Mapper tool.
The testis specificity index was calculated from modENCODE tissue expression data by Vedelek et al., 2018 to indicate the degree of testis enrichment compared to other tissues. Scores range from -2.52 (underrepresented) to 5.2 (very high testis bias).
Comment: maternally deposited
Analysis ofchromosome spreads of polytene salivary chromosomes shows that the Su(var)205 (HP1) protein localizes predominately to known heterochromatic regions and regions that are transcriptionally repressed such as band 31 on Chromosome 2L.
JBrowse - Visual display of RNA-Seq signals
View Dmel\Su(var)205 in JBrowse
2-30
2-27.3
2-28.9
2-31.1 +/- 3.1
2-24.7 +/- 1.3
2-28.9 +/- 2.0
2-31.1
Please Note FlyBase no longer curates genomic clone accessions so this list may not be complete
Please Note This section lists cDNAs and ESTs that fall within the genomic extent of the gene model, which may include cDNAs and ESTs of genes within introns, or of overlapping genes. Please see JBrowse for alignment of the cDNAs and ESTs to the gene model.
For each fully sequenced cDNA the DGRC maintains various forms of the cDNA (e.g tagged or untagged) in several different host vectors for subsequent cloning and expression in Drosophila and Drosophila cell lines.
monoclonal
polyclonal
New stable cell line derived from S2-unspecified : Stable S2 cell lines expressing tos and Su(var)205 were created.
New stable cell line derived from S2-unspecified : Stable S2 cell lines were created expressing eyg containing a mutation in the putative motif for interaction with Su(var)205.
DNA-protein interactions: genome-wide binding profile assayed for Su(var)205 protein in Kc167 cells; see Chromatin_types_NKI collection report. Individual protein-binding experiments listed under "Samples" at GEO_GSE22069 (http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE22069).
Expression is enriched in embryonic gonads.
The Su(var)205 protein modulates chromosomal integrity, histone modifications and transcription in a sex-specific manner.
The binding of Su(var)205 protein to many, but not all, target loci is dependent on Su(var)3-9.
Methyl-K9 His3 protein and Su(var)205 protein co-localise to the heterochromatic region of polytene chromosomes.
Su(var)205 may facilitate the coalescence of dispersed middle repetitive sequences, and organise the heterochromatic structure responsible for the variegated silencing of nearby euchromatic genes.
Su(var)205 is required for normal transcriptional activation of heterochromatic genes.
A consensus pentapeptide is sufficient for specific interaction with the Su(var)205 chromo shadow domain. Su(var)205 dimerisation occurs via pentapeptide binding.
Mutations in Su(var)205 suppress telomeric Position Effect Variegation (PEV) on the fourth chromosome, but not the second and third chromosomes.
The Su(var)205 product, HP1, targets the chromatin of transposon insertions and binds more densely at a site with repeated sequences susceptible to heterochromatin formation. Sufficient density of Su(var)205 protein association is a necessary step in heterochromatin formation and gene silencing.
Actr13E colocalises with Su(var)205 in the centric heterochromatin throughout prepupal development and the two proteins undergo a series of changes in nuclear distribution that coincide with major shifts in nuclear functions.
Naturally occurring regulatory P-elements inserted at the telomere of the X chromosome have been isolated in a genomic context devoid of other P-elements. One or two copies of autonomous P-elements at this site (1A) are sufficient to elicit a strong P repression in the germline. Regulatory properties of the P-elements at 1A are strongly impaired by mutation of Su(var)205.
The regulatory properties of P-elements at 1A are affected by mutants at Su(var)205.
Su(var)205 protein contains a second chromo domain-like motif, the 'chromo shadow domain', in the C-terminal part of the protein.
Studies of the embryonic lethality of mutants demonstrates that in addition to its effect on position-effect variegation, Su(var)205 is also required for normal nuclear morphology and mitosis.
The intracellular localisation of Su(var)205 in the diploid nuclei of embryos before and after developmental changes that occur between cycles 10 and 14 is studied.
Point mutations in the chromo domain of Su(var)205 abolish its ability to promote homeotic gene silencing. The chromo domain has chromosome binding activity. Pc also has a chromo domain, a chimeric Su(var)205-Pc protein (the chromo domain of Pc in the context of Su(var)205) causes mislocalisation of Su(var)205 to Pc binding sites and expression in transgenic flies promotes heterochromatin mediated gene silencing. Results support the view that the chromo domain homology reflects a common mechanistic basis for homeotic and heterochromatic silencing.
Su(var)205 is multiply phosphorylated in tissues, predominantly at Ser and Thr residues. Maternally synthesised Su(var)205 protein is under phosphorylated. At 1.5-2 hours of development, when cytologically visible heterochromatin appears, the more phosphorylated Su(var)205 isoforms appear. Results are consistent with a role for phosphorylation of Su(var)205 in the assembly and maintenance of heterochromatin.
Heterochromatin-associated Su(var)205 gene product appears in euchromatic chromosomal regions that are inactivated as a result of position-effect variegation.
Analysis of the subcellular localisation of Ecol\lacZ-Su(var)205 fusion proteins shows that amino acids 152-206 form the nuclear localisation domain and amino acids 95 to 206 form the heterochromatin binding domain of the Su(var)205 protein.
Su(var)205 homologue has been cloned from D.virilis : a high degree of conservation in N- and C-terminal domains of the encoded DNA-binding protein "HP1" suggests that these domains could interact with other macromolecules in the formation of the condensed structure of heterochromatin.
Su(var)205 gene product is an essential protein that functions as a part of an epigenetic mechanism capable of generating and maintaining an inactive chromatin structure.
Alleles show additive effects with mod alleles on suppression of In(1)wm4 position effect variegation.
Su(var)205 protein, detected by the C1A9 antibody in polytene chromosomes, is preferentially located in the beta-heterochromatin, the basal regions of the polytene chromosome arms and throughout chromosome 4.
Triplo-dependent enhancer of variegation.
The variegation enhancer phenotype is due to increase in gene dosage: independently derived duplications of Su(var)205 act as enhancers and reversion of the dominant enhancer phenotype corresponds with the loss of the duplication.
triplo-enhancer; duplications for the locus cause enhancement of variegation (Tartof, Bishop, Jones, Hobbs and Locke, 1989).
Encodes a nonhistone chromosomal protein, which by immunofluorescent staining of polytene chromosomes with a monoclonal antibody, is localized to α, β, and intercalary heterochromatin as well as chromosome 4 (FBrf0045031).
