RNP-1, an RNA-binding motif is conserved in the DNA-binding cold shock domain

Sequence analysis has shown that there is a short motif of 8 amino acids, corresponding to the RNP-1 motif found in canonical RNA-binding domains, which is common to two families of apparently unrelated proteins. Many RNA-binding proteins contain the RNP-1 and RNP-2 motifs in an RNA-binding domain. The cold shock domain (CSD) family of proteins, which includes several transcription factors which have been shown to bind to DNA, has now been identified to contain a motif similar to RNP-1. A non-redundant protein sequence database was searched with regular expressions and with a weight/residue position matrix of the RNP-1 motif resulting in the identification of numerous known members of the RNA-binding family of proteins. In addition, the search identified that the CSD-containing family of proteins includes a motif which is almost identical to the RNP-1 motif. A determination of the statistical significance of this analysis showed that the RNP-1 motifs from these two families of proteins are indeed similar.