REAGENT or RESOURCE	SOURCE	IDENTIFIER
Antibodies
Mouse anti-FLAG (HRP conjugate)	Sigma	Cat#A8592; RRID:AB_439702
Rabbit anti-INTS4	Abcam	Cat#ab75253; RRID:AB_1280962
Rabbit anti-INTS11	Cusabio	Cat#PA722574ESR1HU; RRID:AB_2888982
Rabbit anti-GAPDH	ProteinTech	Cat#10494-1-AP; RRID:AB_2263076
Mouse anti-SBP	EMD Millipore	Cat#MAB10764; RRID:AB_10631872
Goat anti-Rabbit	Abcam	Cat#ab205718; RRID:AB_2819160
Mouse anti-HA (HRP-Conjugate)	Santa Cruz	Cat#SC7392HRP; RRID:AB_627809
Goat anti-Mouse	Thermo Fisher	Cat#31430; RRID:AB_228307
Bacterial and virus strains
NEB10	NEB	Cat# C3020K
DH10EMBacY	Bieniossek et al., 2012	N/A
Chemicals, peptides, and recombinant proteins
RNAiMAX	Invitrogen	Cat#13778030
L-Glutamine	GIBCO	Cat#A29168-01
Penicillin-Streptomycin (10,000 U/mL)	GIBCO	Cat#15140-122
DMEM	GIBCO	Cat#31966-021
ExpressFive™ SFM	GIBCO	Cat#10486025
SF-900™ II SFM	GIBCO	Cat#11497013
Opti-MEM	GIBCO	Cat#31985-062
Trypsin-EDTA	GIBCO	Cat#25200-056
FBS	GIBCO	Cat#10270-106
LipoD293	Sinagen	Cat#SL100668
PEI 25k	Polysciences	Cat#23966-1
Tween20	Sigma	Cat#P1379-500ML
Freestyle™ 293 Expression Medium	GIBCO	Cat#12338018
Glutaraldehyde	Sigma Aldrich	Cat#G5882-10X1ML
Triton X-100	ICN Biomedicals	Cat#807426
Pierce™ ECL Western Blotting Substrate	Thermo Fisher	Cat#32209
Immobilon Membrane	Merck	Cat#PVH000010
Anti-FLAG Resin	Sigma Aldrich	Cat#F2426-1ML
Anti-HA Resin	Sigma Aldrich	Cat#A2905-1ML
High Capacity Streptavidin Agarose Resin	Thermo Fisher	Cat#20361
His60 Ni Superflow Resin	Takara	Cat#635660
IgG Sepharose™ 6 Fast Flow	GE Healthcare	Cat#17-0969-01
Amylose Resin	NEB	Cat#E8021S
Deposited data
High-resolution cryo-EM map	This paper	EMDB: EMD-12165
Medium-resolution cryo-EM map	This paper	EMDB: EMD-12166
INTS4-focused cryo-EM map	This paper	EMDB: EMD-12164
CTD2-focused cryo-EM map	This paper	EMDB: EMD-12163
Model refined against high-resolution map	This paper	PDB: 7BFP
Pseudoatomic model fitted into medium-resolution map	This paper	PDB: 7BFQ
Experimental models: cell lines
HEK293T	ATCC	Cat#CRL-3216
FreeStyle™ 293-F	GIBCO	Cat#R79007
SF21	GIBCO	Cat#11497013
Trichoplusia ni High Five Cells	Invitrogen	Cat#B85502
Oligonucleotides
INTS4 siRNA (5′-GUAGGCUUAAGGAGUAUGUGAUU-3′)	Dharmacon, based on Albrecht et al. (2018)	N/A
INTS11 siRNA (5′-CAGACUUCCUGGACUGUGUUU-3′)	Dharmacon, based on Albrecht et al. (2018)	N/A
Scrambled siRNA control (5′-UGCACCGAGUGGCGACACCUU-3′)	this study	N/A
Recombinant DNA
pBIG1a+8xHis-INTS4/INTS9/SBP-INTS11	this study	N/A
pBIG1a+8xHis-INTS5/SBP-INTS8	this study	N/A
pBIG1c+8xHis-INTS10/INTS13/SBP-INTS14	this study	N/A
pMG-3xFLAG+INTS11	this study	N/A
pMG-3xFLAG+INTS11ΔCTD2	this study	N/A
pMG-3xFLAG+INTS11ΔCTD1ΔCTD2	this study	N/A
pMG-3xFLAG+INTS11ΔCTD1	this study	N/A
pMG_3xFLAG+INTS11H480P/T482P	this study	N/A
pMG-3xFLAG+INTS11V454P/G455P	this study	N/A
pMG-3xFLAG+INTS11F490P/L492P	this study	N/A
pMG-3xFLAG+INTS11K462E	this study	N/A
pMG-3xFLAG+INTS11R510P/T512P	based on Wu et al. (2017)	N/A
pMG-3xFLAG+INTS11E203Q	based on Baillat et al. (2005)	N/A
pMG-SBP+INTS4K122A/H124A/Q125A	this study	N/A
pMG-SBP+INTS4H164A/R167A	this study	N/A
pMG-SBP+INTS4R210A	this study	N/A
Software and algorithms
PyMol	N/A	https://pymol.org/2/
Coot	Emsley and Cowtan, 2004	https://www2.mrc-lmb.cam.ac.uk/personal/pemsley/coot/
CCPEM	Burnley et al., 2017	https://www.ccpem.ac.uk/
Relion	Scheres, 2012	https://www3.mrc-lmb.cam.ac.uk/relion/
UCSF ChimeraX	Goddard et al., 2018	https://www.cgl.ucsf.edu/chimerax/
Image Lab	Bio-Rad	http://www.bio-rad.com/en-fr/product/image-lab-software?ID=KRE6P5E8Z
Fiji		https://imagej.net/Fiji
MARS	BMG Labtech	https://www.bmglabtech.com/de/mars-datenanalyse-software/
Promals3D	Pei et al., 2008	http://prodata.swmed.edu/promals3d/promals3d.php
Other
UltrAuFoil R1.2/1.3 300 mesh	Quantifoil	Cat#Q350AR13A
Superose 6 3.2/300 Increase	GE Healthcare	Cat#GE29-0915-98
Vitribot Mark IV	Thermo Fisher Scientific	https://www.thermofisher.com/us/en/home.html
Amicon-Ultra 0.5 ml Centrifugal filters – 50 kDa	Merck	UFC5050
96-well plate, black	Corning	Cat#3925
CLARIOstar	BMG Labtech	https://www.bmglabtech.com/clariostar-plus/
ChemiDoc MP	Bio-Rad	http://www.bio-rad.com/en-us/category/chemidoc-imaging-systems?ID=NINJ0Z15
Vibra Cell VCX750	Sonics	https://www.sonics.com/liquid-processing/products/vibra-cell-processors/vcx-500-vcx-750/