Crystallization and preliminary crystallographic analysis of eukaryotic transcription and mRNA export factor Iws1 from Encephalitozoon cuniculi

Abstract

Transcription elongation by eukaryotic RNA polymerase II requires the coupling of mRNA synthesis and mRNA processing and export. The essential protein Iws1 is at the interface of these processes through its interaction with histone chaperone and elongation factor Spt6 as well as with complexes involved in mRNA processing and export. Upon crystallization of the evolutionarily conserved domain of Iws1 from Encephalitozoon cuniculi, four different crystal forms were obtained. Three of the crystal forms belonged to space group P2(1) and one belonged to space group P222(1). Preliminary X-ray crystallographic analysis of one of the crystal forms allowed the collection of data to 2.5 A resolution.

Figure 1

Purified ecIws1_55–198 protein. Molecular-mass markers are shown in the left lane and their corresponding masses are given in kDa.

Figure 2

Different crystal forms obtained upon crystallization of ecIws1_55–198. (a) Form I (space group P2₁). (b) Form II (space group P222₁). (c) Form III (space group P2₁). (d) Form IV (space group P2₁). The black bars represent 100 µm.

Figure 3

Diffraction pattern obtained with crystal form IV (space group P2₁). The resolution rings displayed are at 40.0, 20.0, 8.0, 4.0 and 2.5 Å.