Chromosomal protein HMG-14. Complete human cDNA sequence and evidence for a multigene family.
The isolation and sequencing of cDNA clone coding for the entire sequence of human nonhistone chromosomal protein HMG-14 is described. Sequence analysis reveals that the open reading frame constitutes only 25% of the transcript, that the 5'-untranslated region is extremely rich in GC residues (75%), and that the 3'-untranslated region is highly enriched in AT residues. The amino acid sequence, deduced from the reading frame, is 94% homologous to the calf thymus protein suggesting evolutionary constraints on the conformation of the protein. The human genome contains 60-90 HMG-14 gene copy equivalents which, as suggested by Southern analysis, are not tandemly arranged. Northern analysis of RNA isolated from several sources reveals that a single-sized mRNA codes for this protein. Southern analysis reveals that cross-hybridizing sequences are present in the genome of several different species indicating that the evolutionary origin of this gene was over 350 million years ago. The overall features of the human HMG-14 cDNA are very similar to those of the human HMG-17 cDNA, and the number of gene equivalents present in the human genome is similar for the two proteins. However, their nucleotide sequence is significantly different indicating that the multigene family coding for HMG-14 is distinct from that coding for HMG-17.