A direct interaction between the Utp6 HAT domain and a specific peptide in Utp21 is essential for efficient pre-rRNA processing.
September 08, 2008
Champion EA, Lane BH, Jackrel ME, Regan L, Baserga SJ.Mol Cell Biol. 2008 Aug 25. [Epub ahead of print]
The SSU processome is a ribosome biogenesis intermediate that assembles from its subcomplexes onto the pre-18S rRNA with yet unknown order and structure. Here, we investigate the architecture of the UtpB subcomplex of the SSU processome, focusing on the interaction between the HAT domain of Utp6 and a specific peptide in Utp21. We present a comprehensive map of the interactions within the UtpB subcomplex, and further show that the N-terminal domain of Utp6 interacts with Utp18, while the HAT domain interacts with Utp21. Using a panel of point and deletion mutants of Utp6, we show that an intact HAT domain is essential for efficient pre-rRNA processing and cell growth. Further investigation of the Utp6-Utp21 interaction using both genetic and biophysical methods shows that the HAT domain binds a specific peptide ligand in Utp21, the first example of a HAT domain peptide ligand, with a dissociation constant of 10 microM.