Zooming in on Transcription Preinitiation

Class II gene transcription commences with the assembly of the Preinitiation Complex (PIC) from a plethora of proteins and protein assemblies in the nucleus, including the General Transcription Factors (GTFs), RNA polymerase II (RNA pol II), co-activators, co-repressors and more. TFIID, a megadalton-sized multiprotein complex comprising 20 subunits is among the first GTFs to bind the core promoter. TFIID assists in nucleating PIC formation, completed by binding of further factors in a highly regulated step-wise fashion. Recent results indicate that TFIID itself is built from distinct pre-formed submodules, which reside in the nucleus but also in the cytosol of cells. Here we highlight recent insights in transcription factor assembly and the regulation of transcription preinitiation.