Heterochromatin Protein 1, alpha (HP1a, Antigen p25, Chromobox Homolog 5 (Drosophila), Cbx5, HP1Hs-alpha)

Heterochromatin protein-1 (HP1) is a methyl-lysine binding protein localized at heterochromatin sites, where it mediates gene silencing. It has been shown that mammalian methyltransferases that selectively methylate histone H3 on lysine-9 generate a binding site for HP1 proteins, a family of heterochromatic adaptor molecules implicated in both gene silencing and supranucleosomal chromatin structure. High-affinity in vitro recognition of a methylated histone H3 peptide by HP1 requires a functional chromodomain. Thus, the HP1 chromodomain is a specific interaction motif for the methyl epitope on lysine-9 of histone H3. \n\nIn vivo, heterochromatin association of HP1 proteins is lost in Suv39h double-null primary mouse fibroblasts but is restored after reintroduction of a catalytically active SUV39H1 HMTase. A molecular mechanism through which the SUV39H-HP1 methylation system can contribute to the propagation of heterochromatic subdomains in native chromatin has been defined. It has been demonstrated that HP1 can bind with high affinity to histone H3 methylated at lysine-9 but not at lysine-4. The chromodomain of HP1 as its methyl-lysine-binding domain has been identified. A point mutation in the chromodomain, which destroys the gene silencing activity of HP1 in Drosophila, abolished methyl-lysine-binding activity. Genetic and biochemical analysis in S. pombe showed that the methylase activity of Clr4 (the SUV39H1 homolog) is necessary for the correct localization of Swi6 (the HP1 equivalent) at centromeric heterochromatin and for gene silencing. A stepwise model for the formation of a transcriptionally silent heterochromatin: SUV39H1 places a methyl marker on histone H3, which is then recognized by HP1 through its chromodomain has been suggested. This model may also explain the stable inheritance of the heterochromatic state. SUV39H1 and HP1 are both involved in the repressive functions of the retinoblastoma protein. Rb associates with SUV39H1 and HP1 in vivo by means of its pocket domain. SUV39H1 cooperates with Rb to repress the cyclin E promoter, and in fibroblasts that are disrupted for SUV39H1, the activity of the cyclin E and cyclin A2 genes are specifically elevated. The SUV39H1-HP1 complex is not only involved in heterochromatic silencing but also has a role in repression of euchromatic genes by Rb and perhaps other corepressor proteins.\n\nApplications:\nSuitable for use in ELISA, Immunohistochemistry and Western Blot. Other Applications not tested.\n\nRecommended Dilutions:\nELISA: 1:128,000\nImmunohistochemistry (paraffin): 2-3ug/ml\nWestern Blot: 0.03-0.1ug/ml\nOptimal dilutions to be determined by the researcher\n\nPositive Control:\nHuman fibroblast A431 and HeLa cell lysates. \n\nStorage and Stability:\nMay be stored at 4 degrees C for short-term only. For long-term storage and to avoid repeated freezing and thawing, aliquot and store at -20 degrees C. Aliquots are stable for at least 12 monthsat -20 degrees C. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap. Further dilutions can be made in assay buffer.\n\nPeptide Blocking:\nCorresponding peptide is available for Peptide Blocking studies. See H2034-50D-P. Antibody

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SPECIFICATIONS

Catalog Number

H2034-50D

Size

100ug

Applications

ELISA, IHC, WB

Hosts

Goat

Reactivities

Hum

Form

Supplied as a liquid in Tris, pH 7.3, 0.5% BSA, 0.02% sodium azide.

P Type

Pab

Purity

Purified by affinity chromatography.

Isotype

IgG

References

Rohr O, Lecestre D, Chasserot-Golaz S, Marban C, Avram D, Aunis D, Leid M, Schaeffer E. Recruitment of Tat to heterochromatin protein HP1 via interaction with CTIP2 inhibits human immunodeficiency virus type 1 replication in microglial cells. J Virol. 2003 May;77(9):5415-27.

Additional Info

Recognizes human CBX5 at ~22kD. Species sequence homology: mouse, canine, chinese hamster.