A transcription regulator activity that modulates the transcription of specific gene sets via binding to a DNA-binding transcription factor at a specific genomic locus, either on its own or as part of a complex. Coregulators often act by altering chromatin structure and modifications. For example, one class of transcription coregulators modifies chromatin structure through covalent modification of histones. A second class remodels the conformation of chromatin in an ATP-dependent fashion. A third class modulates interactions of DNA-bound DNA-binding transcription factors with other transcription coregulators. [ http://en.wikipedia.org/wiki/Transcription_coregulator http://www.ncbi.nlm.nih.gov/pubmed/16858867 http://www.ncbi.nlm.nih.gov/pubmed/25957681 http://www.ncbi.nlm.nih.gov/pubmed/10213677 http://www.ncbi.nlm.nih.gov/pubmed/24203923 GOC:txnOH-2018 ]