Cytoplasmic binding partners of the Integrator endonuclease INTS11 and its paralog CPSF73 are required for their nuclear function.

INTS11 and CPSF73 are metal-dependent endonucleases for Integrator and pre-mRNA 3′-end processing, respectively. Here, we show that the INTS11 binding partner BRAT1/CG7044, a factor important for neuronal fitness, stabilizes INTS11 in the cytoplasm and is required for Integrator function in the nucleus. Loss of BRAT1 in neural organoids leads to transcriptomic disruption and precocious expression of neurogenesis-driving transcription factors. The structures of the human INTS9-INTS11-BRAT1 and Drosophila dIntS11-CG7044 complexes reveal that the conserved C terminus of BRAT1/CG7044 is captured in the active site of INTS11, with a cysteine residue directly coordinating the metal ions. Inspired by these observations, we find that UBE3D is a binding partner for CPSF73, and UBE3D likely also uses a conserved cysteine residue to directly coordinate the active site metal ions. Our studies have revealed binding partners for INTS11 and CPSF73 that behave like cytoplasmic chaperones with a conserved impact on the nuclear functions of these enzymes. [Display omitted] • BRAT1/CG7044 is a binding partner that stabilizes INTS11 in the cytoplasm • BRAT1/CG7044 is required for Integrator function in the nucleus • The conserved C terminus of BRAT1-CG7044 is captured in the INTS11 active site • UBE3D is a binding partner of CPSF73 with a similar mechanism of action Lin et al. reveal BRAT1/CG7044 as a binding partner for the INTS11 endonuclease that behaves like a cytoplasmic chaperone and is required for Integrator function in the nucleus. UBE3D is also identified as a binding partner for the CPSF73 endonuclease in pre-mRNA 3′-end processing, with a similar mechanism of action. [ABSTRACT FROM AUTHOR]