Short Communication

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Abstract
Outer dense fibers (ODF) or accessory fibers are filamentous structures of the sperm tail of many eumetozoan organisms endowed with internal fecundation. The bovine and porcine cDNA of an outer dense fiber protein was cloned, sequenced and compared to the previously characterized human and rat cDNA sequences. The coding sequences and the 5' and 3' untranslated regions of the ODF cDNAs are highly conserved. A comparison of the bovine, porcine, human and rat ODF protein sequences revealed that the protein displays a high degree of similarity, ranging from 87% to 98%. The ODF protein is rich in cysteine and contains the C.X.P. repeat at the C-terminal which is different in number among mammalian species. All the 27 cysteine residues in the ODF sequence except those in the C.X.P. repeat are conserved in the four species. We report here also the organization of the bovine ODF gene which is similar to that of human and rat. The transcription start site in the bovine ODF gene is localized 98 bp upstream of the translation start site. Alignment of the 5' flanking region of bovine ODF with the rat gene reveals that the first 130 nucleotides upstream of the transcription start site exhibit an overall sequence similarity of 83%. This conserved region contains a TATA-like box (TTTAAA) and binding sites for AFT/CREB and EGR-1 transcription factors.