title: Reevaluation of the predicted gene structure of Dictyostelium cystatin A3 (cpiC) by nucleotide sequence determination of its cDNA* and its phylogenetic position in the cystatin superfamily.
abstract: Cystatins, cysteine protease inhibitors, are widely distributed among eukaryotes. We reevaluated the structure of the gene cpiC, a gene encoding the third identified member of cystatin family (cystatin A3) that was predicted in the genome database of the social amoeba Dictyostelium discoidium (dictyBase) but remained controversial. We determined the sequences of cDNA and PCR-amplified genomic DNA fragment and found a critical error in the registered nucleotide sequence. The corrected cystatin A3 gene has an open reading frame (ORF) without intron sequence interruption and encodes 94 amino acids (aa), in contrast to the previously predicted sequence of either 80, 82 or 118 aa. The cDNA has an unusual internal poly(A) sequence of 31 adenines, which immediately follows the translation termination codon (TAA) located 146 nucleotides upstream of the post-transcriptional polyadenylation site. The amino acid sequence of Dictyostelium cystatin A3 shows a high similarity to those of previously reported Dictyostelium cystatins as well as Family I cystatins of higher eukaryotes.
authors.affiliation: Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan.
authors.forename: Medhat S
authors.initials: MS
authors.lastname: El-Halawany
authors.forename: Hideki
authors.initials: H
authors.lastname: Shibata
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Hitomi
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Maki
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016000:Cluster Analysis; D015891:Cystatins / Q000235:genetics*; D017931:DNA Primers; D018076:DNA, Complementary / Q000235:genetics; D004023:Dictyostelium / Q000235:genetics*; D040461:Gene Components; D008969:Molecular Sequence Data; D010802:Phylogeny; D011061:Poly A / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D015891:Cystatins; D017931:DNA Primers; D018076:DNA, Complementary; D011061:Poly A