Ribosome assembly factors Pwp1 and Nop12 are important for folding of 5.8S rRNA during ribosome biogenesis in Saccharomyces cerevisiae.

Previous work from our lab suggests that a group of interdependent assembly factors (A3 factors) is necessary to create early, stable pre-ribosomes. Many of these proteins bind at or near ITS2, but in their absence ITS1 is not removed from rRNA, suggesting long-range communication between these two spacers. By comparing ...
the non-essential assembly factors Nop12 and Pwp1 we show that misfolding of rRNA is sufficient to perturb early steps of biogenesis, but it is the lack of the A3 factors that results in turnover of early pre-ribosomes. Deletion of NOP12 significantly inhibits 27SA3 pre-rRNA processing, even though the A3 factors are present in pre-ribosomes. Furthermore, pre-rRNAs are stable indicating the block in processing is not sufficient to trigger turnover. This is in contrast to the absence of Pwp1, in which the A3 factors are not present and pre-rRNAs are unstable. In vivo RNA structure probing revealed that the pre-rRNA processing defects are due to misfolding of 5.8S rRNA. In the absence of Nop12 and Pwp1, rRNA helix 5 is not stably formed. Interestingly, the absence of Nop12 results in the formation of an alternative, yet unproductive helix 5 when cells are grown at low temperatures.
Mol. Cell. Biol.
Date: Mar. 17, 2014
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