Updated publication reference for PubMed record(s): 31988137. Updated publication reference for DOI(s): 10.1038/s41591-019-0738-2. Chemical cross-linking coupled to mass spectrometry was used to study binary and ternary complexes involving cyclin-dependent kinase 8 (CDK8), cyclin-C, and subunit 12 of the Mediator complex (MED12). Cross-linking was performed using different cross-linking chemistries: (1) disuccinimidyl suberate (DSS); (2) a combination of pimelic acid dihydrazide (PDH) and the coupling reagent, DMTMM.