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.

Department of Cell Biology Faculty of Science Charles University Prague 12800 Czech Republic

Department of Molecular and Cellular Biology Center for Precision Environmental Health and Dan L Duncan Comprehensive Cancer Center Baylor College of Medicine Houston TX 77030 USA

Molecular Virology and Gene Therapy KU Leuven Molecular Virology and Gene Therapy Leuven 3000 Flanders Belgium

Protein Structure Characterization by Advanced Mass Spectrometry Institute of Microbiology of the CAS Prague 14220 Czech Republic

Structural Biology Institute of Molecular Genetics of the CAS Prague 14220 Czech Republic

Structural Biology Institute of Organic Chemistry and Biochemistry of the CAS Prague 16000 Czech Republic

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