ABSTRACT
The extraordinary rate of progress in the study of eukaryotic gene control processes can be gauged from the fact that by 1980, no transcriptional regulatory protein or its DNA-binding site in a regulated gene promoter had been defined. Clearly therefore, the process by which a single agent can activate a specific transcription factor and thereby modulate gene expression was reasonably well understood in outline by 1990. The case of the thyroid hormone receptor illustrates two of the major themes to have emerged in recent years from further study of gene control processes, namely the role of co-repressor/co-activator molecules and the influence of transcription factors on chromatin structure. The chromatin structure and hence the transcription of the genes encoding the homeodomain factors themselves are subject to regulation by the polycomb and trithorax proteins. In general therefore, a variety of different analyses indicate the enormous complexity of gene regulatory processes.
