Molecular Mechanism of LEDGF/p75 Dimerization.

Dimerization of many eukaryotic transcription regulatory factors is critical for their function. Regulatory role of an epigenetic reader lens epithelium-derived growth factor/p75 (LEDGF/p75) requires at least two copies of this protein to overcome the nucleosome-induced barrier to transcription elongation. Moreover, various LEDGF/p75 binding partners are enriched for dimeric features, further underscoring the functional regulatory role of LEDGF/p75 dimerization. Here, we dissected the minimal dimerization region in the C-terminal part of LEDGF/p75 and, using paramagnetic NMR spectroscopy, identified the key molecular contacts that helped to refine the solution structure of the dimer. The LEDGF/p75 dimeric assembly is stabilized by domain swapping within the integrase binding domain and additional electrostatic "stapling" of the negatively charged α helix formed in the intrinsically disordered C-terminal region. We validated the dimerization mechanism using structure-inspired dimerization defective LEDGF/p75 variants and chemical crosslinking coupled to mass spectrometry. We also show how dimerization might affect the LEDGF/p75 interactome. • Full-length LEDGF/p75 forms dimers with a low micromolar K D • LEDGF/p75 residues 345–467 is the minimal stable dimerization domain • LEDGF dimer is stabilized by domain swapping and additional electrostatic stapling • LEDGF dimerization does not impair binding of interaction partners Dimerization is an important process regulating eukaryotic transcription. Lux et al. use a combination of biophysical and biochemical techniques to investigate the dimerization mechanism of LEDGF/p75, the H3K36 methylation reader, and its effect on molecular interactions with other proteins. [ABSTRACT FROM AUTHOR]