The product of unr, the highly conserved gene upstream of N-ras, contains multiple repeats similar to the cold-shock domain (CSD), a putative DNA-binding motif.

We show that the open reading frame transcribed from the unr gene (immediately upstream of N-ras) in mammals consists of multiple repeats similar to the cold-shock domain (CSD), a putative DNA-binding motif found in prokaryotic cold-shock proteins, and eukaryotic DNA-binding proteins. Alignment of the CSD sequences of unr with those from other proteins reveals a core of similarity for which a consistent secondary structure prediction can be derived. This prediction suggests that the CSD consists primarily of beta-sheet, in contrast to most known eukaryotic DNA-binding proteins. Sequence analysis of the 3' end of the guinea pig unr gene shows that the core of one CSD repeat is encoded in a single exon, consistent with the modular assembly of the gene from ancestral CSD-coding units.