A novel growth-inducible gene that encodes a protein with a conserved cold-shock domain.

We have isolated a cDNA that encodes a novel member of the Y-box binding protein family, termed as RYB-a (Rat Y-box Binding protein-a). RYB-a is a 31 kDa protein that contains a conserved cold-shock domain and an amino acid alignment similar to those of charge zipper proteins. Expression of RYB-a mRNA was highly abundant in the skeletal muscle, spleen, and fetal liver. The expression is very low in new-born and adult livers, suggesting its expression is under developmental regulation. In addition, the expression of RYB-a mRNA was induced in the liver during regeneration and by stimulation of quiescent fibroblast cells with serum. Induction in the fibroblasts was inhibited by treating the cell with a specific tyrosine kinase inhibitor, genistein or by detachment of cell-adhesion. Since both treatments are known to inhibit G1 cells to enter S phase, RYB-a gene is thought to be a member of growth-inducible genes.