Primary structure and developmental expression of Bufo arenarum cellular nucleic acid-binding protein: Changes in subcellular localization during early embryogenesis

A Bufo arenarum cellular nucleic acid-binding protein (bCNBP) full-length c DNA was cloned. bCNBP is a 19.4 kDa protein containing seven CCHC zinc fing er motifs, an RGG box and a Ser-rich region. Amino acid comparisons showed high values of homology in vertebrates and smaller values in insects or inf erior eukaryotes. Northern blot analysis during oogenesis and early develop ment revealed two transcripts with different expressions of pattern behavio r. One of them is present in all stages analyzed, whereas the other is only detected from the beginning of zygotic transcription. Immunocytochemistry assays carried out on sections of ovary and early embryos showed that there was no specific staining of previtellogenic oocytes. In early vitellogenic oocytes, in oocytes at stages V/VI and in embryos at early blastula stage, reaction was observed inside the cytoplasm. At mid-blastula stage, CNBP wa s mainly detected in the epiblast. At the late gastrula stage, two layers o f cells were stained in the archenteron roof, in which the internal one pre sented as strong staining. Nuclei in this layer were stained even stronger than the cytoplasm. Changes in mRNA expression patterns, accompanied by cha nges in subcellular localization, suggest that CNBP might interact with bot h nuclear and cytoplasmic nucleic acids.