Crystallization of the Oct-1/SNAP190 peptide/DNA complex

Crystals of the Oct-1 POU/SNAP190 peptide/DNA tertiary complex have been obtained by hanging-drop vapor diffusion at 293 K in 20% 2-propanol, 20% PEG 4000 and 0.1 M sodium citrate pH 5.6. The Oct-1 POU protein has two domains, one a homeodomain and the other a POU domain, which are connected by a flexible linker. The DNA used in the complex is slightly different in the octamer region compared with the two previously crystallized Oct-1 POU/DNA complexes. The DNA is 14 base pairs, with an octamer sequence of 5′-­ATGTAGAT-3′ and an overhang of one base on both strands. The SNAP190 peptide is 27 amino acids long (residues 884–910). The crystals diffract to 2.3 Å (94.1% completeness) at the synchrotron under cryogenic (123 K) conditions. The crystals are triclinic, space group P1, with unit-cell parameters a = 36.4, b = 54.9, c = 77.6 Å, α = 94.9, β = 99.6, γ = 109.2°. This structure will provide insight into how Oct-1 interacts with SNAP190, a critical component of the small nuclear RNA-activating protein complex (SNAPc). Transcription of human snRNA genes is activated by these direct protein–protein interactions.