Gene

Cell biology

Biology

General transcription factor

RNA polymerase II

Transcription factor II A

Promoter

TATA-Box Binding Protein

Computational biology

ChIA-PET

Transcription factor II F

Genetics

Chromatin

Transcription preinitiation complex

Transcription factor II E

RNA polymerase II holoenzyme

Transcription factor II D

Transcription factor II B

Nucleosome

Gene expression

Molecular Cell

Transcription initiation by RNA polymerase II (RNA Pol II) requires preinitiation complex (PIC) assembly at gene promoters. In the dynamic nucleus, where thousands of promoters are broadly distributed in chromatin, it is unclear how multiple individual components converge on any target to establish the PIC. Here we use live-cell, single-molecule tracking in S. cerevisiae to visualize constrained exploration of the nucleoplasm by PIC components and Mediator's key role in guiding this process. On chromatin, TFIID/TATA-binding protein (TBP), Mediator, and RNA Pol II instruct assembly of a short-lived PIC, which occurs infrequently but efficiently within a few seconds on average. Moreover, PIC exclusion by nucleosome encroachment underscores regulated promoter accessibility by chromatin remodeling. Thus, coordinated nuclear exploration and recruitment to accessible targets underlies dynamic PIC establishment in yeast. Our study provides a global spatiotemporal model for transcription initiation in live cells.

Spatiotemporal coordination of transcription preinitiation complex assembly in live cells