Abstract

In eukaryotic cells, heterochromatin is typically composed of tandem DNA repeats and plays crucial roles in gene expression and genome stability. It has been reported that silencing at individual units within tandem heterochromatin repeats exhibits a position‐dependent variation. However, how the heterochromatin is organized at an individual repeat level remains poorly understood. Using a novel genetic approach, our recent study identified a conserved protein Rex1BD required for position‐dependent silencing within heterochromatin repeats. We further revealed that Rex1BD interacts with the 14‐3‐3 protein to regulate heterochromatin silencing by linking RNAi and HDAC pathways. In this review, we discuss how Rex1BD and the 14‐3‐3 protein coordinate to modulate heterochromatin organization at the individual repeat level, and comment on the biological significance of the position‐dependent effect in heterochromatin repeats. We also identify the knowledge gaps that still need to be unveiled in the field.