DKC1 and hyperinsulinemic hypoglycemia, familial, 4: Box H/ACA small nucleolar ribonucleoproteins (snoRNAs) play a nonnegligible role in rRNA pseudouridylation.461,470,471 snoRNA can also regulate rRNA folding.472,473 In addition, Cbf5p (dyskerin) depletion also causes pre-rRNA processing defects similar to snR30 depletion.474 One study found that dyskerin deficiency in human cells results in defective rRNA uridine modification, altering ribosome activity.475,476 The gene encoding dyskerin is well-known as DKC1, and mutations in this gene can lead to Ψ deficiency and cause X-linked keratosis congenital.