A nuclear protein in Schizosaccharomyces pombe with homology to the human tumour suppressor Fhit has decapping activity.
Authors
Salehi, ZivarGeffers, Lars
Vilela, Cristina
Birkenhäger, Ralf
Ptushkina, Marina
Berthelot, Karine
Ferro, Myriam
Gaskell, Simon J
Hagan, Iain M
Stapley, Ben
McCarthy, John E G
Affiliation
Department of Biomolecular Sciences, UMIST, PO Box 88, Manchester M60 1QD, UK.Issue Date
2002-10
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A number of eukaryotic proteins are already known to orchestrate key steps of mRNA metabolism and translation via interactions with the 5' m7GpppN cap. We have characterized a new type of histidine triad (HIT) motif protein (Nhm1) that co-purifies with the cap-binding complex eIF4F of Schizosaccharomyces pombe. Nhm1 is an RNA-binding protein that binds to m7GTP-Sepharose, albeit with lower specificity and affinity for methylated GTP than is typical for the cap-binding protein known as eukaryotic initiation factor 4E. Sequence searches have revealed that proteins with strong sequence similarity over all regions of the new protein exist in a wide range of eukaryotes, yet none has been characterized up to now. However, other proteins that share specific motifs with Nhm1 include the human Fhit tumour suppressor protein and the diadenosine 5', 5"'-P1, P4-tetraphosphate asymmetrical hydrolase of S. pombe. Our experimental work also reveals that Nhm1 inhibits translation in a cell-free extract prepared from S. pombe, and that it is therefore a putative translational modulator. On the other hand, purified Nhm1 manifests mRNA decapping activity, yet is physically distinct from the Saccharomyces cerevisiae decapping enzyme Dcp1. Moreover, fluorescence and immunofluorescence microscopy show that Nhm1 is predominantly, although not exclusively, nuclear. We conclude that Nhm1 has evolved as a special branch of the HIT motif superfamily that has the potential to influence both the metabolism and the translation of mRNA, and that its presence in S. pombe suggests the utilization of a novel decapping pathway.Citation
A nuclear protein in Schizosaccharomyces pombe with homology to the human tumour suppressor Fhit has decapping activity. 2002, 46 (1):49-62 Mol. Microbiol.Journal
Molecular MicrobiologyDOI
10.1046/j.1365-2958.2002.03151.xPubMed ID
12366830Type
ArticleLanguage
enISSN
0950-382Xae974a485f413a2113503eed53cd6c53
10.1046/j.1365-2958.2002.03151.x
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