Heterochromatin protein 1 (HP1a in Drosophila) is a conserved eukaryotic 
chromosomal protein that is prominently associated with pericentric 
heterochromatin and mediates the concomitant gene silencing. Mechanistic studies 
implicate HP1 family proteins as 'hub proteins,' able to interact with a variety 
of chromosomal proteins through the chromo-shadow domain (CSD), as well as to 
recognize key histone modification sites [primarily histone H3 di/trimethyl Lys9 
(H3K9me2/3)] through the chromodomain (CD). Consequently, HP1 has many important 
roles in chromatin architecture and impacts both gene expression and gene 
silencing, utilizing a variety of mechanisms. Clearly, HP1 function is altered 
by context, and potentially by post-translational modifications (PTMs). Here, we 
report on recent ideas as to how this versatile protein accomplishes its diverse 
functions.