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H/ACA ribonucleoprotein complex subunit 2

Known also as: Nucleolar protein family A member 2, snoRNP protein NHP2

Known abbreviations: NHP2, NOLA2, HSPC286


Required for ribosome biogenesis and telomere maintenance. Part of the 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. May also be required for correct processing or intranuclear trafficking of TERC, the RNA component of the telomerase reverse transcriptase (TERT) holoenzyme.

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).

Subcellular location

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

Tissue specificity

Expressed in brain, colon, heart, kidney, ovary, pancreas, placenta, prostate, skeletal muscle, small intestine, spleen, testis and thymus. Also expressed at lower levels in the liver.

Developmental stage

Transcript peaks at G1/S transition.

Involvement in disease

Dyskeratosis congenita, autosomal recessive, 2: A rare multisystem disorder caused by defective telomere maintenance. It is characterized by progressive bone marrow failure, and the clinical triad of reticulated skin hyperpigmentation, nail dystrophy, and mucosal leukoplakia. Common but variable features include premature graying, aplastic anemia, low platelets, osteoporosis, pulmonary fibrosis, and liver fibrosis among others. 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.

Sequence similarities

Belongs to the ribosomal protein L7Ae family.

Activities in which H/ACA ribonucleoprotein complex subunit 2 is involved: Pathways in which H/ACA ribonucleoprotein complex subunit 2 is involved:

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

Links to other databases:

Database ID Link
Uniprot Q9NX24 Q9NX24
KEGG hsa:55651 hsa:55651
PFAM: PF01248
InterPro: IPR002415
CATH: - -
SCOP: - -

Protein sequence:

H/ACA ribonucleoprotein complex subunit 2 (Homo sapiens) is product of expression of NHP2 ribonucleoprotein gene.

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Last modification of this entry: May 1, 2013.

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