Heterochromatin Protein 1, gamma (HP1g, M32), phosphorylated (Ser83)

Heterochromatin protein 1 (HP1) is a family of heterochromatic adaptor molecules involved in both gene silencing and higher order chromatin structure (1). All three HP1 family members (a, b and g) are primarily associated with centromeric heterochromatin; however, HP1b and g also localize to euchromatic sites in the genome (2,3). HP1 proteins are approximately 25kD in size and each contains a conserved amino-terminal chromodomain, followed by a variable hinge region and a conserved carboxy-terminal chromoshadow domain. The chromodomain facilitates binding to histone H3 tri-methylated on Lys9, a histone "mark" closely associated with centromeric heterochromatin (4,5). The variable hinge region binds both RNA and DNA in a sequence-independent manner (6). The chromoshadow domain mediates the dimerization of HP1 proteins, in addition to binding multiple proteins implicated in gene silencing and heterochromatin formation, including the SUV39H histone methyltransferase, the DNMT1 and DNMT3a DNA methyltransferases and the p150 subunit of chromatin-assembly factor-1 (CAF1) (7-9). In addition to contributing to heterochromatin formation and propagation, HP1 and SUV39H are also found complexed with retinoblastoma (Rb) and E2F6 proteins, both of which function to repress euchromatic gene transcription in quiescent cells (10,11). HP1 proteins are subject to multiple types of post-translational modifications, including phosphorylation, acetylation, methylation, ubiquitination and sumoylation, suggesting multiple means of regulation (12-14). HP1g is phosphorylated on Ser83 by protein kinase A (PKA) in vitro, and activation of PKA by forskolin and IBMX treatment leads to increased phosphorylation in vivo (14). Phosphorylation of HP1g on Ser83 also increases in mitosis as demonstrated by our Phospho-HP1g (Ser83) Antibody, which shows increased immunofluorescent staining in untreated mitotic cells and increased Western blot signal in lysates from cells arrested in mitosis by treatment with paclitaxel. Phosphorylation of Ser83 only occurs on a subpopulation of HP1g found associated with euchromatin,\n\nApplications: \nSuitable for use in Immunofluorescence, Western Blot and Immunoprecipitation. Other applications not tested.\n\nRecommended Dilution:\nImmunofluorescence: 1:200\nWestern Blot: 1:1000\nImmunoprecipitation: 1:25\nOptimal dilutions to be determined by the researcher.\n\nStorage and Stability:\nFor long-term storage, aliquot and store at -20 degrees C. Aliquots are stable for at least 12 months at -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.

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SPECIFICATIONS

Catalog Number

H2034-53

Size

100ul

Applications

IF, IP, WB

Hosts

Rabbit

Reactivities

Hum, Mouse, Rat, NHP

Form

Supplied as a liquid in 10 mM HEPES (pH 7.5), 150 mM NaCl, 100ug/ml BSA and 50% glycerol.

P Type

Pab

Purity

Purified by immunoaffinity chromatography.

Isotype

IgG

References

(1) Maison, C. and Almouzni, G. (2004) Nat. Rev. Mol. Cell Biol. 5, 296

Additional Info

Binds to coding regions of active genes (14). This phosphorylation impairs the ability of HP1g to silence transcription and may be a marker for transcription elongation (14).