Biology:Dyskerin

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H/ACA ribonucleoprotein complex subunit 4 is a protein that in humans is encoded by the DKC1 gene.[1][2][3] The encoded protein, known as dyskerin, is a highly conserved nucleolar enzyme that plays key roles in rRNA modification, telomerase function, and ribosome biogenesis.

Structure

Dyskerin is an L-shaped protein consisting of approximately 514 amino acid residues, with a molecular weight of about 58 kilo-daltons.[4] It belongs to the TruB family of pseudouridine synthase enzymes and forms the catalytic core of the H/ACA box snoRNP (small nucleolar ribonucleoprotein) complex. The DKC1 gene is located on the X chromosome, in a tail-to-tail orientation with the gene encoding palmitoylated erythrocyte membrane protein 1 (MPP1), and is transcribed in a telomere-to-centromere direction.[3]

Function

The DKC1 gene encodes a core component of the H/ACA snoRNP complex, which also includes the NOLA1, NOLA2, and NOLA3 proteins. These proteins localize to the dense fibrillar components of nucleoli and to coiled (Cajal) bodies in the nucleus. The H/ACA snoRNPs catalyze pseudouridylation of rRNA and are essential for proper ribosome biogenesis. Depletion of any of the four core proteins impairs 18S rRNA production and pseudouridylation.[3]

Beyond rRNA modification, dyskerin contributes to several other fundamental processes. It stabilizes the telomerase RNA component (TERC), thereby maintaining telomerase activity and ensuring telomere elongation and genomic stability.[4] Dyskerin also participates in the assembly and maturation of ribosomal subunits by promoting correct folding and processing of pre-rRNA intermediates. In addition, it has been implicated in the regulation of pre-mRNA splicing, potentially through interactions with small Cajal body-specific RNAs (scaRNAs) that guide pseudouridylation of spliceosomal RNAs.[4]

The human protein is homologous to Saccharomyces cerevisiae Cbf5p and Drosophila melanogaster Nop60B proteins, indicating strong evolutionary conservation.[3]

Clinical significance

Mutations in DKC1 cause X-linked dyskeratosis congenita, a rare inherited disorder characterized by defective telomere maintenance, premature aging, bone marrow failure, and increased cancer susceptibility.[1][2][3] Both nucleotide substitutions and trinucleotide repeat polymorphisms have been identified in this gene. The pathogenic variants typically impair dyskerin function, disrupting rRNA modification and telomerase RNA stability, leading to the disease phenotype.

Mutations in DKC1 are also associated with Hoyeraal-Hreidarsson syndrome.[5]

References

  1. ↑ 1.0 1.1 "X-linked dyskeratosis congenita is caused by mutations in a highly conserved gene with putative nucleolar functions". Nature Genetics 19 (1): 32–38. May 1998. doi:10.1038/ng0598-32. PMID 9590285. 
  2. ↑ 2.0 2.1 "Mapping and characterization of the X-linked dyskeratosis congenita (DKC) gene". Genomics 55 (1): 21–27. January 1999. doi:10.1006/geno.1998.5600. PMID 9888995. 
  3. ↑ 3.0 3.1 3.2 3.3 3.4 "Entrez Gene: DKC1 dyskeratosis congenita 1, dyskerin". https://www.ncbi.nlm.nih.gov/gene?Db=gene&Cmd=ShowDetailView&TermToSearch=1736. 
  4. ↑ 4.0 4.1 4.2 "Dyskerin: an essential pseudouridine synthase with multifaceted roles in ribosome biogenesis, splicing, and telomere maintenance". RNA 27 (12): 1441–1458. December 2021. doi:10.1261/rna.078953.121. PMID 34556550. 
  5. ↑ "Hoyeraal-Hreidarsson syndrome with a DKC1 mutation identified by whole-exome sequencing". Gene 546 (2): 425–429. August 2014. doi:10.1016/j.gene.2014.06.011. PMID 24914498. 

Further reading



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