Transcription Factor Dynamics.

The regulation of gene transcription in eukaryotic systems involves a large number of factors. These proteins have been argued to form large, relatively long lived, multi-protein complexes on promoter elements during the process of transcription initiation and elongation. Recent advances in imaging technology have permitted for the first time a dissection of transcription events in real time. Using arrays of gene reporter elements and transcripiton factors tagged with the green fluorescent protein, it is now possible to observe targeting of a regulatory protein to response elements in living cells. Application of photobleaching technology to these systems allows a direct analysis of the rate at which factors are moving in the nucleoplasmic space, and the timing of their interactions with various intranuclear structures, including DNA regulatory sites. These technical breakthroughs have led to the unexpected finding that most transcription factors interact very briefly with promoter elements, and cycle on and off genes at relatively high rates. These findings stand in dramatic contrast to the classic view of large, static initiation complexes, and reveal a level of dynamic action not previously suspected in the process of transcriptional regulation. [ABSTRACT FROM AUTHOR]