Cells have a recurrent need for the correct assembly of protein-nucleic acid complexes. We have studied a yeast homolog of the smallest subunit of chromatin assembly factor 1 (CAF1), encoded by YMR131c and termed "RRB1". Unlike other yeast homologs, Msi1p, and Hat2p, Rrb1p is essential for cell viability. Impairment of Rrb1p function results in decreased levels of free 60S ribosomal subunits and the appearance of half-mer polysomes, suggesting its involvement in ribosome biogenesis. Using tandem affinity purification (TAP ) combined with mass spectrometry, we show that Rrb1p is associated with ribosomal protein L3. A fraction of Rrb1p is also found in a protein-precursor rRNA complex containing at least ten other early-assembling ribosomal proteins. We propose that Rrb1p is required for proper assembly of preribosomal particles during early ribosome biogenesis, presumably by targeting L3 onto the 35S precursor rRNA. This action may resemble the mechanism by which CAF1 assembles histones H3/H4 onto newly replicated DNA.
SciCrunch is a data sharing and display platform. Anyone can create a custom portal where they can select searchable subsets of hundreds of data sources, brand their web pages and create their community. SciCrunch will push data updates automatically to all portals on a weekly basis. User communities can also add their own data to SciCrunch, however this is not currently a free service.