One of the most fundamental processes of life is protein synthesis by the ribosome. Although much is known about the function and structure of this macromolecular complex, our understanding on its assembly is still vague. In this issue of The EMBO Journal, Malyutin et al (2017) provide a detailed picture of one of the latest assembly stages of the yeast 60S ribosomal subunit. The cryo‐EM map of the 60S‐Nmd3‐Lsg1‐Tif6 complex sheds new light on the function of Nmd3, Lsg1 and Tif6—and their release mechanisms—right before the 60S subunit joins the pool of actively translating ribosomes.
See also: AG Malyutin et al and
C Ma et al
The eukaryotic ribosome consists of four ribosomal RNA molecules (rRNA) and ~80 ribosomal proteins (r‐proteins). These components are organized into the 40S small and 60S large subunits that associate forming the 80S ribosome. Ribosome assembly starts in the nucleus and is completed in the cytoplasm, with immature particles exported from the nucleus to the cytoplasm during this process. Assembly of the eukaryotic ribosome involves more than 200 biogenesis factors that support folding, processing and modifications of the rRNA, enable nuclear export of the assembling ribosomal particles or functionally test the active sites of the subunits (Karbstein, 2013; Woolford & Baserga, 2013; Greber, 2016). The general mechanisms by which these factors perform their functions remain poorly understood.
Pioneering work from the Hurt and Beckman's laboratories (Bradatsch et al, 2012) provided the first moderate resolution (11.9 Å) cryo‐EM reconstruction of a pre‐60S particle revealing how multiple assembly factors bind immature ribosomal particles. The recent introduction …
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