Zebrafish cellular nucleic acid binding protein: developmental expression pattern and function

WEINER,A. M. J.; ARMAS, P.; LOMBARDO, V. A.; ALLENDE, M. A.; CALCATERRA, N. B.

Guaruja, San Pablo

Congreso; 2nd International Meeting of the Latin American Society of Developmental Biology (LASDB); 2005

Sociedad latinoameroicana de Biología del desarrollo (LASDB)

Cellular nucleic acid binding protein (CNBP) is a small single-stranded nucleic acid binding protein strikingly conserved among vertebrates, which biological function is not completely known. Cellular functions assigned to CNBP range from transcriptional regulation to translational control. It consists of seven CCHC zinc knuckles and an RGG box between the first two zinc knuckles. We analysed the zebrafish CNBP (zCNBP) gene and expression. zCNBP gene is organised in five exons and four introns as all the CNBP genes reported for vertebrates. It is noteworthy the absence of a predicted promoter region. zCNBP-mRNA expression was high in ovary and during the first developmental stages. Its levels decreased while early development progressed until the mid-blastula transition (MBT) and increased again thereafter. The zCNBP-mRNA distribution was homogeneous in the embryo up to the 24 hpf stage. The protein showed a differential subcellular localization pattern. It is cytoplasmic in pre-MBT blastomeres and becomes nuclear at post-MBT developmental stages. We also analysed zCNBP in vivo function by transient modification of the embryonic zCNBP by morpholynos, mRNA, protein, and anti-CNBP antibody microinjections. Changes of the maternal zCNBP caused sever malformations in the posterior trunk and tail development, while reduction of embryonic zCNBP induced abnormal formation of the midbrain/hindbrain border. Besides zCNBP binding to single-stranded DNA and RNA probes, it is also able to act as a nucleic acid chaperone by promoting the annealing of complementary oligonucleotides in vitro. Hence, CNBP is a strikingly conserved single-stranded nucleic acid binding protein which might interact with cytoplasmic maternal mRNA during the development first stages, perhaps influencing the expression of proteins involved in the tail formation. CNBP becomes nuclear once MBT takes place possibly in order to modulate zygotic transcription and/or to associate with newly synthesised transcripts, probably affecting the expression of zygotic gene involved in the midbrain/hindbrain differentiation. In all these regulative processes CNBP may act as a nucleic acid chaperone by binding, remodelling and stabilizing nucleic acids secondary structures.