Cover image

Cover The Drosophila PIWI protein directly interacts with heterochromatin protein 1a (HP1a). Shown here are top (left) and side (right) views of an NMR-based model of the HP1a dimer (green and blue) binding to an N-terminal PIWI peptide (magenta), with only the PxVxV-binding motif of the peptide shown. The interaction occurs between a PxVxV motif centered on V30 of the PIWI N-terminal domain and the dimerized interface of the chromoshadow domain (CSD) of HP1a. Side chains of the conserved residues (P, V, V) are displayed. Residues of HP1a that interact with PIWI are colored in dark green and dark blue. Mutating the V30 residue to alanine abolishes PIWI-HP1a interaction. (For details, see Brower-Toland et al., p. 2300.)