Gene

Cytoplasm

Cell biology

Linguistics

Phase (matter)

Helicase

Philosophy

Molecular biology

Biology

Processivity

Transcription (linguistics)

Biochemistry

RNA Helicase A

RNA polymerase III

Nucleolus

RNA polymerase I

Organic chemistry

Polymerase

Chemistry

RNA polymerase

Science

RNA polymerase I (Pol I) transcription takes place at the border of the fibrillar center (FC) and the dense fibrillar component (DFC) in the nucleolus. Here, we report that individual spherical FC/DFC units are coated by the DEAD-box RNA helicase DDX21 in human cells. The long noncoding RNA (lncRNA) SLERT binds to DDX21 RecA domains to promote DDX21 to adopt a closed conformation at a substoichiometric ratio through a molecular chaperone-like mechanism resulting in the formation of hypomultimerized and loose DDX21 clusters that coat DFCs, which is required for proper FC/DFC liquidity and Pol I processivity. Our results suggest that SLERT is an RNA regulator that controls the biophysical properties of FC/DFCs and thus ribosomal RNA production.

lncRNA <i>SLERT</i> controls phase separation of FC/DFCs to facilitate Pol I transcription

lncRNA SLERT controls phase separation of FC/DFCs to facilitate Pol I transcription