DnaJ/HSP40 Homolog Subfamily C, Member 21 (DNAJC21)

The Hsp40 chaperone Jjj1 is required for the nucleo-cytoplasmic recycling of preribosomal factors in Saccharomyces cerevisiae. The absence of Jjj1 leads to a cold sensitive phenotype, a defect in the relative amount of the large ribosomal subunit with the appearance of halfmers, and to cytoplasmic accumulation of shuttling factors such as Arx1 and Alb1, which stay bound to the pre-60S particles. Jjj1 is a novel pre-60S factor involved in the last cytoplasmic steps of the large ribosomal subunit biogenesis. The biochemical association of Jjj1 and Rei1 to similar pre-60S complexes, their two-hybrid interactions, and their functional links. Rei1 and Jjj1 share many common features. Jjj1 is preferentially required for the release of Arx1 and Alb1 shuttling factors from the cytoplasmic pre-60S particles while Rei1 is preferentially involved in their recycling.