Bcp 1 is the Nuclear Chaperone of the 60 S ribosomal protein Rpl 23 in Saccharomyces cerevisiae

Eukaryotic ribosomes are composed of rRNAs and ribosomal proteins. Ribosomal proteins are translated in the cytoplasm and imported into the nucleus for assembly with the rRNAs. It has been shown that chaperones or karyopherins responsible for import can maintain the stability of ribosomal proteins by neutralizing unfavorable positive charges and thus facilitate their transports. Among 79 ribosomal proteins in yeast, only few are identified with specific chaperones. Besides the classic role in maintaining protein stability, chaperones have additional roles in transport, chaperoning the assembly site, and dissociation of ribosomal proteins from karyopherins. Bcp1 has been shown necessary for the export of Mss4, a PI4P 5-kinase, and required for ribosome biogenesis. However, its specific function in ribosome biogenesis was not described. Here, we show that Bcp1 dissociates Rpl23 from the karyopherins and associates with Rpl23 afterward. Loss of Bcp1 causes instability of Rpl23 and deficiency of 60S Bcp1 is the Nuclear Chaperone of the 60S ribosomal protein Rpl23 in Saccharomyces cerevisiae Ya-Han Ting 1 , Ting-Jun Lu 1 , Arlen W. Johnson 2 , Jing-Ting Shie, Bo-Ru Chen 1 , Suresh Kumar.S 1,3 , Kai-Yin Lo †1