The function of DNAJC21 (DnaJ heat shock protein family (Hsp40) member C21, Ensembl gene identifier ENSG00000168724) is as follows. May act as a co-chaperone for HSP70. May play a role in ribosomal RNA (rRNA) biogenesis, possibly in the maturation of the 60S subunit. Binds the precursor 45S rRNA. .