SPT5 stabilizes RNA polymerase II, orchestrates transcription cycles, and maintains the enhancer landscape

Transcription progression is governed by multitasking regulators including SPT5,
an evolutionarily conserved factor implicated in virtually all transcriptional steps from
enhancer activation to termination. Here we utilize a rapid degradation system and
reveal crucial functions of SPT5 in maintaining cellular and chromatin RNA polymerase
II (Pol II) levels. Rapid SPT5 depletion causes a pronounced reduction of paused Pol II
at promoters and enhancers, distinct from NELF degradation resulting in short-distance
paused Pol II redistribution. Most genes exhibit downregulation but not upregulation,
accompanied by greatly impaired transcription activation, altered chromatin landscape
at enhancers, and severe Pol II processivity defects at gene bodies. Phosphorylation of
an SPT5 linker at serine 666 potentiates pause release and is antagonized by
Integrator-PP2A (INTAC) targeting SPT5 and Pol II, while phosphorylation of SPT5
C-terminal region links to 3' end termination. Our findings position SPT5 as an
essential positive regulator of global transcription.