the formation of ribosomal subunits occurs at the nucleolus.
the formation of ribosomal subunits occurs at the nucleolus.
where does the formation of ribosomal subunits occur?
nucleolus
when observed under the electron microscope, the nucleolus can be seen to consist of three distinguishable regions: the innermost "fibrillar centers" (fcs), surrounded by the "dense fibrillar component" (dfc) (that contains fibrillarin and nucleolin), which in turn is bordered by the "granular component" (gc) (that contains the protein nucleophosmin). transcription of the rdna occurs either in the fc or at the fc-dfc boundary, and, therefore, when rdna transcription in the cell is increased, more fcs are detected. most of the cleavage and modification of rrnas occurs in the dfc, while the latter steps involving protein assembly onto the ribosomal subunits occur in the gc.
cell nucleus
in case of tcp-seq, ribosomes and ribosomal subunits engaged in interaction with mrna are first fast chemically crosslinked to it with formaldehyde to preserve existing state of interactions (“snapshot” of distribution) and to block any possible non-equilibrium processes. the crosslinking can be performed directly in, but not restricted to, live cells. the rna is then partially degraded ("e.g." with ribonuclease) so that only fragments protected by the ribosomes or ribosomal subunits are left. the protected fragments are then purified according to the sedimentation dynamics of the attached ribosomes or ribosomal subunits, de-blocked, sequenced and mapped to the source transcriptome, giving the original locations of the translation complexes over mrna.
tcp-seq