Interaction between Ribosome Assembly Factors Krr1 and Faf1 is Essential for Formation of Small Ribosomal Subunit in Yeast [Protein Structure and Folding]

July 2nd, 2014 by Zheng, S., Lan, P., Liu, X., Ye, K.

Ribosome formation in Saccharomyces cerevisiae requires a large number of transiently associated assembly factors that coordinate processing and folding of pre-rRNA and binding of ribosomal proteins. Krr1 and Faf1 are two interacting proteins present in early 90S precursor particles of small ribosomal subunit. Here we determine a co-crystal structure of the core domain of Krr1 bound to a 19-residue fragment of Faf1 at 2.8 Å resolution. The structure reveals that Krr1 consists of two packed K homology (KH) domains, KH1 and KH2, and resembles archaeal Dim2-like proteins. We show that KH1 is a divergent KH domain that lacks the RNA-binding GXXG motif and is involved in binding another assembly factor, Kri1. KH2 contains a canonical RNA-binding surface and additionally associates with an α-helix of Faf1. Specific disruption of Krr1-Faf1 interaction impaired early 18S rRNA processing at sites A0, A1 and A2 and caused cell lethality, but it did not prevent incorporation of the two proteins into preribosomes. The Krr1-Faf1 interaction likely maintains a critical conformation of 90S preribosomes required for pre-rRNA processing. Our results illustrate the versatility of KH domains in protein interaction and provide insight into the role of Krr1-Faf1 interaction in ribosome biogenesis.
  • Posted in Journal of Biological Chemistry, Publications
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