Emerging insights into the function and structure of the Integrator complex.

The Integrator was originally discovered as a specialized 3'-end processing endonuclease complex required for maturation of RNA polymerase II (RNAPII)-dependent small nuclear RNAs (snRNAs). Since its discovery, Integrator's spectrum of substrates was significantly expanded to include non-polyadenylated long noncoding RNAs (lncRNA), enhancer RNAs (eRNAs), telomerase RNA (tertRNA), several Herpesvirus transcripts, and messenger RNAs (mRNAs). Recently emerging transcriptome-wide studies reveled an important role of the Integrator in protein-coding genes, where it contributes to gene expression regulation through promoter-proximal transcription attenuation. These new functional data are complemented by several structures of Integrator modules and higher-order complexes, providing mechanistic insights into Integrator-mediated processing events. In this work, we summarize recent progress in our understanding of the structure and function of the Integrator complex.