EXTREME EVOLUTIONARY CONSERVATION OF QM, A NOVEL C-JUN ASSOCIATED TRANSCRIPTION FACTOR

QM is a 214 amino acid polypeptide, encoded by a gene (DXS648) in Xq28 , that contains a high percentage of charged amino acids and has been found to bind c-Jun and DNA. Searches of the GenBank database revealed no matches between QM and any other known transcription factors. Howe ver, we and others have isolated QM homologs from a diverse array of e ukaryotes. Alignment of these sequences indicated a high degree of con servation throughout the first 175 residues of the protein and reveale d several interesting features. Most notable is the considerable conse rvation of charged amino acids within specific regions of the protein. Secondary structure analysis suggests that two of these regions form amphipathic alpha-helices, one basic and one acidic. A third conserved charged domain, comprising the N-terminal 30 amino acids, is both bas ic and proline rich. The rate of sequence divergence of the various ho mologs was found to be slow (of the order of 1% change every 22 millio n years), consistent with a critical role for QM in eukaryotic cells. A role for QM as a novel class of transcription regulatory protein is suggested.