Facts about FACT and transcript elongation through chromatin

The regulation of transcription elongation within the context of chromatin is a topic of great interest. Even though chromatin presents a barrier to transcription by the PoIII machinery in vitro, this process is rather efficient in vivo. Importantly, the chromatin structure of the actively transcribed genes is altered as part of this process. A large number of factors implicated in the control of transcript elongation have been identified through genetics, biochemistry and targeted proteomics approaches. However the precise roles and mechanisms of action of these factors remain obscure. A significant advance came about this past year with the elucidation of the roles of FACT and Spt6 in transcription elongation. These factors facilitate PoIII passage through chromatin by destabilizing the nucleosome structure as well as reassemble nucleosomes traversed by PoIII.