Cloning of the chicken chromosomal protein HMG-14 cDNA reveals a unique protein with a conserved DNA binding domain

The isolation and sequencing of a cDNA clone coding for the entire sequence of chicken chromosomal protein HMG-14 is described. The open reading frame constitutes only 25% of the transcript; the 5'-untranslated region is extremely rich in GC residues; and the 3'-untranslated region is highly enriched in AT residues. Comparison with other cDNAs coding for HMG-14 and HMG-17 reveals that the transcripts of genes coding for this family of chromosomal proteins have a characteristic structure. The deduced amino acid sequence is unique and different from all other known HMG-14 and -17 sequences. Analysis of amino acid position identity between the chicken HMG-14 and other HMG-14/-17 proteins revealed that the protein has 37% similarity to the HMG-17 group and 69% similarity to the HMG-14 group; therefore, the protein is classified as belonging to the HMG-14 group. Additional analysis leads to the conclusion that the chicken cDNA described here codes for the true homolog of calf and human HMG-14 protein. Comparison of all the known HMG-14 sequences reveals the DNA binding domain is conserved and contains the invariant dodecapeptide PKRRSARLSAKP. The HMG-14 proteins have a distinct charge distribution along the polypeptide chain: while the central region is positively charged the C-terminal domain is negatively charged.