PCAF HAT domain dimer detected by chemical cross-linking. A) Chemical cross-linking of the full-length PCAF HAT domain (amino acids 493-658). WT represents the full-length wt PCAF HAT domain (lanes 1-2). LV512DD is a full-length HAT domain with L512D and V516D double mutations (lanes 3-4). LMV512AAA is a full-length HAT domain with L512A/M513A/V516A triple mutations (lanes 5-6). F539A is a full-length HAT domain with single F539 to alanine mutation (lanes 7-8). B) Cross-linking of a shortened PCAF HAT domain (amino acids 496-658) in comparison with a full-length PCAF HAT domain mutant. LVF512DDA is a combined mutant of LV512DD and F539A in the full-length PCAF HAT domain (lanes 3-4). LV2DD is a double mutation (L512D and V516D) in the shortened PCAF HAT domain (lanes 5-6) while LVF2DDA is a triple mutation (L512D, V516D and F539A) in the shortened HAT domain (lanes 7-8). The arrows indicate monomer (black), dimer (green) and higher oligomers (red). Lanes where DSS was added are indicated above the gel and M denotes a protein molecular weight marker.