Table 1.

Cryo-EM data collection, refinement and validation statistics

	U1-OC (EMDB-15009, PDB 7ZXE)	U1-OC, local map (EMDB-15007, PDB-7ZX8)	U1-CC (EMDB-15006, PDB-7ZX7)	U5-CC (EMDB-14997, (PDB-7ZWD)	U5-CC, local map (EMDB-14996, PDB- 7ZWC)
Data collection and processing
Magnification		×81,000		×81,000
Voltage (kV)		300		300
Electron exposure (e–/Å2)		54.45		51.93
Defocus range (μm)		−0.5 to −3.0		−0.5 to −2.5
Pixel size (Å)		1.05		1.05
Micrographs collected		16,854		4,842
Initial particle images (no.)		5,181,947		1,299,523
Final particle images (no.)	137,246	137,246	47,293	85,787	85,787
Map resolution (Å)	3.0	3.5	3.4	3.0	3.2
FSC threshold	0.143	0.143	0.143	0.143	0.143
Map resolution range (Å)	2.8–5.2	3.4–6.0	3.0–7.0	2.75–5.25	3.0–5.0
Refinement
Initial model used (PDB code)	7NVU	7NVU	7NVS	7NVS	7NVS
Map sharpening B factor (Å2)	−10	−10	−5	−10	−10
Model composition
DNA	126	93	132	132	83
Protein residues	5,842	1,500	5,789	5,789	1,500
Ligands	11	2	12	12	2
B factors (Å2)
DNA	276.52	174.43	318.34	248.19	95.70
Protein residues	133.43	186.65	215.69	124.47	109.50
Ligands	192.93	155.55	237.49	194.42	82.54
R.m.s. deviations
Bond lengths (Å)	0.005	0.003	0.004	0.007	0.003
Bond angles (°)	0.755	0.606	0.509	0.658	0.524
Validation
MolProbity score	1.78	1.68	1.69	1.63	1.67
Clashscore	9.52	8.46	9.85	7.55	7.63
Poor rotamers (%)	0.16	0.00	0.00	0.00	0.00
CaBLAM outliers	1.93	1.73	1.63	1.91	2.07
Cβ outliers	0.00	0.00	0.00	0.00	0.00
Ramachandran plot
Favored (%)	95.91	96.61	97.03	96.68	96.27
Allowed (%)	4.09	3.39	2.97	3.32	3.73
Disallowed (%)	0.00	0.00	0.00	0.00	0.00