J. Maceluch et al., Cloning and characterization of Arabidopsis thaliana AtNAP57 - a homologueof yeast pseudouridine synthase Cbf5p, ACT BIOCH P, 48(3), 2001, pp. 699-709
Rat Nap57 and its yeast homologue Cbf5p are pseudouridine synthases involve
d in rRNA biogenesis, localized in the nucleolus. These proteins, together
with H/ACA class of snoRNAs compose snoRNP particles, in which snoRNA guide
s the synthase to direct site-specific pseudouridylation of rRNA. In this p
aper we present an Arabidopsis thaliana protein that is highly homologous t
o Cbf5p (72% identity and 85% homology) and NAP57 (67% identity and 81% hom
ology). Moreover, the plant protein has conserved structural motifs that ar
e characteristic features of pseudouridine synthases of the TruB class. We
have named the cloned and characterized protein AtNAP57 (Arabidopsis thalia
na homologue of NAP57). AtNAP57 is a 565 amino-acid protein and its calcula
ted molecular mass is 63 kDa. The protein is encoded by a single copy gene
located on chromosome 3 of the A. thaliana genome. Interestingly, the AtNAP
57 gene does not contain any introns. Mutations in the human DKC1 gene enco
ding dyskerin (human homologue of yeast Cbf5p and rat NAP57) cause dyskerat
osis congenita a rare inherited bone marrow failure syndrome characterized
by abnormal skin pigmentation, nail dystrophy and mucosal leukoplakia.