The HP1 chromo shadow domain binds a consensus peptide pentamer

Abstract

Heterochromatin-associated protein 1 (HP1) is thought to affect chromatin structure through interactions with other proteins in heterochromatin. Chromo domains located near the amino (amino chromo) and carboxy (chromo shadow) termini of HP1 may mediate such interactions, as suggested by domain swapping, in vitro binding and 3D structural studies . Several HP1-associated proteins have been reported, providing candidates that might specifically complex with the chromo domains of HP1. However, such association studies provide little mechanistic insight and explore only a limited set of potential interactions in a largely non-competitive setting. To determine how chromo domains can selectively interact with other proteins, we probed random peptide phage display libraries using chromo domains from HP1. Our results demonstrate that a consensus pentapeptide is suffident for specific interaction with the HP1 chromo shadow domain. The pentapeptide is found in the amino acid sequence of reported HP1-associated proteins, including the shadow domain itself. Peptides that bind the shadow domain also disrupt shadow domain dimers. Our results suggest that HP1 dimerization, which is thought to mediate heterochromatin compaction and cohesion, occurs via pentapeptide binding. In general, chromo domains may function by avidly binding short peptides at the surface of chromatin-associated proteins.

Diverse roles of HP1 proteins in heterochromatin assembly and functions in fission yeast

“…This disparity could be because of limited interaction of factors such as Epe1, Mis4, Hsk1-Dbf1, and HDACs with Swi6 in the context of constitutive heterochromatin representing a small fraction of total chromatin. Another difference is that Motamedi et al (59) purified Swi6 tagged at its carboxy-terminus, which contains the chromoshadow domain implicated in dimerization and interactions of HP1 proteins with other factors (11,12). In this regard, we note that amino-terminal TAP-tagged Swi6 purified in our study is functional, and interacts with TGS and chromosome segregation factors linked to heterochromatin biology.…”

“…H3K9me has an important role in targeting HP1 family proteins that bind to methylated H3 tail via their amino-terminal chromodomain (7)(8)(9)(10). HP1 proteins also contain a carboxy-terminal chromoshadow domain that is critical for their dimerization and interactions with diverse factors (11)(12)(13). Indeed, HP1 proteins contribute to diverse chromosomal processes, including silencing of target loci, proper segregation of chromosomes, and developmentally controlled long-range chromatin interactions (1).…”

Isoform-specific interaction of HP1 with human TAF II 130

“…We compared known HP1-interacting proteins and their HP1 boxes with the potential hTAF II 130 HP1 box (ref. 43, Fig. 3B).…”

Drosophila HP1c isoform interacts with the zinc-finger proteins WOC and Relative-of-WOC to regulate gene expression

“…Altogether, these results indicate that HP1c, WOC, and ROW are components of a distinct multiprotein complex. HP1c-WOC interaction is likely to be direct, as WOC contains a canonical PxVxL motif ( 1536 PHVLL 1540 ), which is known to mediate binding to the chromo-shadow domain of HP1 proteins (Lechner et al 2000(Lechner et al , 2005Smothers and Henikoff 2000). This motif is located within the highly conserved C-terminal HC domain of WOC, being also present in the three human homologs.…”