CNBP binds purine-rich ssDNA and its activity depends on the RGG box

ARMAS, P.; NASIF, S.; AGÜERO, T.; AYBAR, M.; CALCATERRA, N. B.

Rosario, Santa Fe, Argentina.

Congreso; XLI Annual Meeting of the Argentine Society for Biochemestry and Molecular Biology Research.; 2006

Sociadad Argentina de Investigacion en Bioquímica y Biología Molecular

Cellular nucleic acid binding protein (CNBP) interacts with single-stranded (ss) nucleic acids. It was implicated in diverse cellular mechanisms of gene expression control during embryo development. Our goal is to identify CNBP nucleic acid targets and characterize its biochemical activity and biological functions. Recombinant Bufo arenarum bCNBP and zebrafish zCNBP were used for gel-shift assays. ssDNA probes were designed by rational mutations of reported targets to identify sequences or secondary structures recognized by CNBP. We conclude that CNBP recognizes probes with ss stretches rich in purine nucleotides. We previously showed that CNBP promotes annealing of complementary DNA strands through the Gly/Arg rich motif (RGG box). Here we show that CNBP is also able to promote nucleic acids melting trough the RGG box. Melting and annealing of nucleic acids are characteristic activities of nucleic acid chaperones, suggesting that CNBP may have this biochemical activity. Finally, CNBP function was analyzed in vivo by microinjecting Xenopus embryos with mRNA coding for wild-type bCNBP and RGG-deletion mutants. Expression of the putative CNBP targets c-Myc and FoxD3 was analyzed by in situ hybridization. Wild-type bCNBP overexpression caused an increase in the expression of analyzed genes while RGG-deletion mutants overexpression decreased the expression of the analyzed genes.