How does the nucleolus fit into ribosome assembly and rrna processing?

[Zachary74]

I’ve been trying to understand the specific role of the nucleolus in ribosome assembly for my cell biology project, but I’m getting tangled up in the difference between transcription of the rRNA genes and the actual processing and assembly stages that happen there. My textbook makes it seem like one seamless process, but the papers I’m reading suggest much more compartmentalization and sequential steps within that dense nuclear region.

[MatthewM]

I kept thinking it would be one smooth flow, but in practice it felt patchy. Transcription happens and then the RNA gets handed off to processing, all within that dense nuclear region, and the proteins come and go while the RNA is trimmed and folded.

[AaronZH]

In reality the rRNA genes are transcribed in the fibrillar center area, early processing happens in the dense fibrillar component, and late ribosome assembly sits in the granular component of the nucleolus. That split always surprised me.

[AddisonP]

Do you think the problem is that the papers are talking about different cell types, or that the compartmentalization is real but not as clean as the diagrams?

[LukeW]

I tried a quick pulse labeling experiment and saw the nascent rRNA appear in one area before processing markers showed up elsewhere, but the timing was loose and variable.