Dataset Information

Heterochromatin Protein 1a (HP1a) partner specificity is determined by critical amino acids in the chromo shadow domain and C-terminal extension.

ABSTRACT: Drosophila melanogaster Heterochromatin Protein 1a (HP1a) is an essential protein critical for heterochromatin assembly and regulation. Its chromo shadow domain (CSD) homodimerizes, a requirement for binding protein partners that contain a PXVXL motif. How does HP1a select among its many different PXVXL-containing partners? HP1a binds tightly to Heterochromatin Protein 2 (HP2), but weakly to PIWI. We investigated differences in homodimerization and the impact of the C-terminal extension (CTE) by contrasting HP1a to its paralogue, HP1b. HP1a and HP1b differ in the dimerization interface, with HP1a having an Arg at position 188 rather than Glu. We find that while this substitution reduces the dimerization constant, it does not impact the binding surface as demonstrated by unchanged partner binding affinities. However, the CTE (only 4 residues in HP1a as compared with 87 residues in HP1b) is critical; the charged residues in HP1a are necessary for tight peptide binding. Examining a panel of amino acid substitutions in the HP1a CSD, we find that Leu-165 in HP1a interacts with HP2 but not PIWI, supporting the conclusion that different sites in the binding surface provide discrimination for partner selection. Partner sequence is also critical for affinity, as the remaining difference in binding between HP2 and PIWI polypeptides is eliminated by swapping the PXVXL motifs between the two. Taken together, these studies indicate that the binding surface of the HP1a CSD plus its short CTE provide the needed discrimination among HP1a's partners, and that the CTE is important for differentiating the interactions of the Drosophila HP1 paralogs.

SUBMITTER: Mendez DL

PROVIDER: S-EPMC3829322 | biostudies-literature | 2013 Aug

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Heterochromatin Protein 1a (HP1a) partner specificity is determined by critical amino acids in the chromo shadow domain and C-terminal extension.

Mendez Deanna L DL Mandt Rebecca E RE Elgin Sarah C R SC

The Journal of biological chemistry 20130623 31

Drosophila melanogaster Heterochromatin Protein 1a (HP1a) is an essential protein critical for heterochromatin assembly and regulation. Its chromo shadow domain (CSD) homodimerizes, a requirement for binding protein partners that contain a PXVXL motif. How does HP1a select among its many different PXVXL-containing partners? HP1a binds tightly to Heterochromatin Protein 2 (HP2), but weakly to PIWI. We investigated differences in homodimerization and the impact of the C-terminal extension (CTE) by ...[more]

PMID: 23793104

Similar Datasets

Project description:BackgroundPseudomonas aeruginosa is a Gram-negative bacterium that causes severe infectious disease in diverse host organisms, including humans. Effective therapeutic options for P. aeruginosa infection are limited due to increasing multidrug resistance and it is therefore critical to understand the regulation of host innate immune responses to guide development of effective therapeutic options. The epigenetic mechanisms by which hosts regulate their antimicrobial responses against P. aeruginosa infection remain unclear. Here, we used Drosophila melanogaster to investigate the role of heterochromatin protein 1a (HP1a), a key epigenetic regulator, and its mediation of heterochromatin formation in antimicrobial responses against PA14, a highly virulent P. aeruginosa strain.ResultsAnimals with decreased heterochromatin levels showed less resistance to P. aeruginosa infection. In contrast, flies with increased heterochromatin formation, either in the whole organism or specifically in the fat body-an organ important in humoral immune response-showed greater resistance to P. aeruginosa infection, as demonstrated by increased host survival and reduced bacterial load. Increased heterochromatin formation in the fat body promoted the antimicrobial responses via upregulation of fat body immune deficiency (imd) pathway-mediated antimicrobial peptides (AMPs) before and in the middle stage of P. aeruginosa infection. The fat body AMPs were required to elicit HP1a-mediated antimicrobial responses against P. aeruginosa infection. Moreover, the levels of heterochromatin in the fat body were downregulated in the early stage, but upregulated in the middle stage, of P. aeruginosa infection.ConclusionsThese data indicate that HP1a-mediated heterochromatin formation in the fat body promotes antimicrobial responses by epigenetically upregulating AMPs of the imd pathway. Our study provides novel molecular, cellular, and organismal insights into new epigenetic strategies targeting heterochromatin that have the potential to combat P. aeruginosa infection.

Dataset Information

Heterochromatin Protein 1a (HP1a) partner specificity is determined by critical amino acids in the chromo shadow domain and C-terminal extension.

Publications

Heterochromatin Protein 1a (HP1a) partner specificity is determined by critical amino acids in the chromo shadow domain and C-terminal extension.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets