ANALYSIS OF THE STRUCTURE AND EXPRESSION OF THE CHICKEN GENE ENCODINGA HOMOLOG OF THE HUMAN RREB-1 TRANSCRIPTION FACTOR

Ras proteins are involved in a number of signal transduction pathways including the mitogen-activated kinase cascade. Activated MAPKs transl ocate to the nucleus and phosphorylate transcription factors such as c -myc, TCF and AP-1. Recently, a Ras-responsive element binding transcr iption factor, RREB-1, was cloned from a human medullary thyroid carci noma cell line. RREB-1 is a zinc finger protein that binds to a Ras-re sponsive element in the promoter of the human calcitonin gene. We repo rt the cloning of the chicken homologue to human RREB-1. Amino-acid al ignment demonstrates that chicken and human RREB-1 are 53% identical a nd 69% similar. Genomic southern analysis indicates that chicken rreb- 1 is a single-copy gene in the chicken genome. We demonstrate that chi cken and human rreb-1 display the same tissue distribution, being expr essed in all tissues examined except the brain. Interestingly, chicken RREB-1 has an extended N-terminus and contains 16 zinc fingers of the TFIIIA subclass, in comparison to human RREB-1 which was reported to contain only four zinc fingers. The size discrepancy between the two p redicted gene products is further discussed. An unusual structural fea ture of RREB-1 is the widely spaced arrangement of the zinc fingers. ( C) 1997 Elsevier Science B.V.