The establishment and maintenance of heterochromatic regions within the genome is an important factor for chromosome stability and con- trolled gene expression. It is dependent on many protein factors that are highly conserved from yeast to human. Among them are HP1 pro- teins that recognize heterochromatin-specific methylation marks and are involved in the recruitment of effector proteins. In my thesis, I will focus on the fission yeast HP1 protein Chp2 and its interaction with the Snf2/HDAC- containing remodeling complex SHREC, a homolog of NuRD complexes in higher organisms. Previously, Chp2 was found to be functionally and biochemically associated with the chromatin remodeler Mit1, a subunit of the SHREC complex. However, details of this interaction were unknown. I was able to solve the structure of the Chp2-Mit1 complex with high resolution and could show that an extensive interface between the two proteins provides high-affinity binding. The data reveals an unusual mode of HP1-client interaction and provides an example how specificity between different HP1 proteins canbe achieved. My work adds to the current knowledge about the highly conserved class of HP1 proteins and deepens our understanding of the molecular basis of their function.