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H/ACA ribonucleoprotein complex subunit 4

 
Known also as: CBF5 homolog, Dyskerin, Nopp140-associated protein of 57 kDa, Nucleolar protein NAP57, Nucleolar protein family A member 4, snoRNP protein DKC1

Known abbreviations: DKC1, NOLA4

Function

Isoform 1: Required for ribosome biogenesis and telomere maintenance. Probable catalytic subunit of H/ACA small nucleolar ribonucleoprotein (H/ACA snoRNP) complex, which catalyzes pseudouridylation of rRNA. This involves the isomerization of uridine such that the ribose is subsequently attached to C5, instead of the normal N1. Each rRNA can contain up to 100 pseudouridine ('psi') residues, which may serve to stabilize the conformation of rRNAs. Also required for correct processing or intranuclear trafficking of TERC, the RNA component of the telomerase reverse transcriptase (TERT) holoenzyme.

Isoform 3: Promotes cell to cell and cell to substratum adhesion, increases the cell proliferation rate and leads to cytokeratin hyper-expression (when overexpressed in HeLa cells).

Catalytic activity

RNA uridine = RNA pseudouridine.

Subunit structure

Part of the H/ACA small nucleolar ribonucleoprotein (H/ACA snoRNP) complex, which contains NHP2/NOLA2, GAR1/NOLA1, NOP10/NOLA3, and DKC1/NOLA4, which is presumed to be the catalytic subunit. The complex contains a stable core formed by binding of one or two NOP10-DKC1 heterodimers to NHP2; GAR1 subsequently binds to this core via DKC1. The complex binds a box H/ACA small nucleolar RNA (snoRNA), which may target the specific site of modification within the RNA substrate. During assembly, the complex contains NAF1 instead of GAR1/NOLA1. The complex also interacts with TERC, which contains a 3'-terminal domain related to the box H/ACA snoRNAs. Specific interactions with snoRNAs or TERC are mediated by GAR1 and NHP2. Associates with NOLC1/NOPP140. H/ACA snoRNPs interact with the SMN complex, consisting of SMN1 or SMN2, GEMIN2/SIP1, DDX20/GEMIN3, and GEMIN4. This is mediated by interaction between GAR1 and SMN1 or SMN2. The SMN complex may be required for correct assembly of the H/ACA snoRNP complex. Component of the telomerase holoenzyme complex at least composed of TERT, DKC1, WRAP53/TCAB1, NOP10, NHP2, GAR1, TEP1, EST1A, POT1 and a telomerase RNA template component (TERC). Interacts with SHQ1; this interaction may lead to the stabilization of DKC1, from the time of its synthesis until its association with NOP10, NHP2, and NAF1 at the nascent H/ACA RNA.

Subcellular location

Isoform 1: Nucleus › nucleolus. Nucleus › Cajal body. Note: Also localized to Cajal bodies (coiled bodies).

Isoform 3: Cytoplasm

Tissue specificity

Ubiquitously expressed.

Involvement in disease

Dyskeratosis congenita, X-linked recessive: A rare, progressive bone marrow failure syndrome characterized by the triad of reticulated skin hyperpigmentation, nail dystrophy, and mucosal leukoplakia. Early mortality is often associated with bone marrow failure, infections, fatal pulmonary complications, or malignancy.
Note: The disease is caused by mutations affecting the gene represented in this entry.

Hoyeraal-Hreidarsson syndrome: A multisystem disorder affecting males and characterized by aplastic anemia, immunodeficiency, microcephaly, cerebellar hypoplasia, and growth retardation.
Note: The disease is caused by mutations affecting the gene represented in this entry.

Sequence similarities

Belongs to the pseudouridine synthase TruB family.

Contains 1 PUA domain.




Activities in which H/ACA ribonucleoprotein complex subunit 4 is involved: Pathways in which H/ACA ribonucleoprotein complex subunit 4 is involved:

NCBI GI number(s): -
Species: Homo sapiens

Links to other databases:

Database ID Link
Uniprot O60832 O60832
BRENDA - -
KEGG hsa:1736 hsa:1736
PFAM: PF08068
PF01472
PF01509
PF08068
PF01472
PF01509
InterPro: IPR012960
IPR002501
IPR020103
IPR002478
IPR015947
IPR004802
IPR004521
IPR012960
IPR002501
IPR020103
IPR002478
IPR015947
IPR004802
IPR004521
CATH: - -
SCOP: - -


Protein sequence:
MADAEVIILPKKHKKKKERKSLPEEDVAEIQHAEEFLIKPESKVAKLDTS
QWPLLLKNFDKLNVRTTHYTPLACGSNPLKREIGDYIRTGFINLDKPSNP
SSHEVVAWIRRILRVEKTGHSGTLDPKVTGCLIVCIERATRLVKSQQSAG
KEYVGIVRLHNAIEGGTQLSRALETLTGALFQRPPLIAAVKRQLRVRTIY
ESKMIEYDPERRLGIFWVSCEAGTYIRTLCVHLGLLLGVGGQMQELRRVR
SGVMSEKDHMVTMHDVLDAQWLYDNHKDESYLRRVVYPLEKLLTSHKRLV
MKDSAVNAICYGAKIMLPGVLRYEDGIEVNQEIVVITTKGEAICMAIALM
TTAVISTCDHGIVAKIKRVIMERDTYPRKWGLGPKASQKKLMIKQGLLDK
HGKPTDSTPATWKQEYVDYSESAKKEVVAEVVKAPQVVAEAAKTAKRKRE
SESESDETPPAAPQLIKKEKKKSKKDKKAKAGLESGAEPGDGDSDTTKKK
KKKKKAKEVELVSE

H/ACA ribonucleoprotein complex subunit 4 (Homo sapiens) is product of expression of dyskeratosis congenita 1, dyskerin gene.



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Last modification of this entry: May 1, 2013.

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