4h7w
From Proteopedia
Crystal Structure of Human C16orf57
Structural highlights
DiseaseUSB1_HUMAN Dyskeratosis congenita;Poikiloderma with neutropenia. Poikiloderma with neutropenia (PN) [MIM:604173: A genodermatosis characterized by poikiloderma, pachyonychia and chronic neutropenia. The disorder starts as a papular erythematous rash on the limbs during the first year of life. It gradually spreads centripetally and, as the papular rash resolves, hypo- and hyperpigmentation result, with development of telangiectasias. Another skin manifestation is pachyonychia, but alopecia and leukoplakia are distinctively absent. Patients have recurrent pneumonias that usually result in reactive airway disease and/or chronic cough. One of the most important extracutaneous symptoms is an increased susceptibility to infections, mainly affecting the respiratory system, primarily due to a chronic neutropenia and to neutrophil functional defects. Bone marrow abnormalities account for neutropenia and may evolve into myelodysplasia associated with the risk of leukemic transformation. Poikiloderma with neutropenia shows phenotypic overlap with Rothmund-Thomson syndrome. Note=The disease is caused by mutations affecting the gene represented in this entry.[1] [2] FunctionUSB1_HUMAN Phosphodiesterase responsible for the U6 snRNA 3' end processing. Acts as an exoribonuclease (RNase) responsible for trimming the poly(U) tract of the last nucleotides in the pre-U6 snRNA molecule, leading to the formation of mature U6 snRNA 3' end-terminated with a 2',3'-cyclic phosphate.[3] [4] Publication Abstract from PubMedThe recessive disorder poikiloderma with neutropenia (PN) is caused by mutations in the C16orf57 gene that encodes the highly conserved USB1 protein. Here, we present the 1.1 A resolution crystal structure of human USB1, defining it as a member of the LigT-like superfamily of 2H phosphoesterases. We show that human USB1 is a distributive 3'-5' exoribonuclease that post-transcriptionally removes uridine and adenosine nucleosides from the 3' end of spliceosomal U6 small nuclear RNA (snRNA), directly catalyzing terminal 2', 3' cyclic phosphate formation. USB1 measures the appropriate length of the U6 oligo(U) tail by reading the position of a key adenine nucleotide (A102) and pausing five uridine residues downstream. We show that the 3' ends of U6 snRNA in PN patient lymphoblasts are elongated and unexpectedly carry non-templated 3' oligo(A) tails that are characteristic of nuclear RNA surveillance targets. Thus, our study reveals a novel quality control pathway in which post-transcriptional 3' end processing by USB1 protects U6 snRNA from targeting and destruction by the nuclear exosome. Our data implicate aberrant oligoadenylation of U6 snRNA in the pathogenesis of the leukemia predisposition disorder PN. Aberrant 3' oligoadenylation of spliceosomal U6 small nuclear RNA in poikiloderma with neutropenia.,Hilcenko C, Simpson PJ, Finch AJ, Bowler FR, Churcher MJ, Jin L, Packman LC, Shlien A, Campbell P, Kirwan M, Dokal I, Warren AJ Blood. 2012 Nov 27. PMID:23190533[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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