Ribosomal protein chaperone involved in large subunit biogenesis; cooperates with Acl1 and binds Rpl1a and Rpl1b; localizes to nucleus and cytosol; localizes to nucleus and cytosol, relocalizes to cytosol under hypoxia; protein abundance increases during DNA replication stress; contains WD-40 domains; BCL1 is not essential in S288C