Transcription coactivator which associates with nuclear receptors, transcriptional coactivators including EP300, CREBBP and NCOA1, and basal transcription factors like TBP and TFIIA to facilitate nuclear receptors-mediated transcription (PubMed:10454579, PubMed:25219498). May thereby play an important role in establishing distinct coactivator complexes under different cellular conditions (PubMed:10454579, PubMed:25219498). Plays a role in thyroid hormone receptor and estrogen receptor transactivation (PubMed:10454579, PubMed:25219498). Also involved in androgen receptor transactivation (By similarity). Plays a pivotal role in the transactivation of NF- kappa-B, SRF and AP1 (PubMed:12077347). Acts as a mediator of transrepression between nuclear receptor and either AP1 or NF-kappa-B (PubMed:12077347). May play a role in the development of neuromuscular junction (PubMed:26924529). May play a role in late myogenic differentiation (By similarity). Also functions as part of the RQC trigger (RQT) complex that activates the ribosome quality control (RQC) pathway, a pathway that degrades nascent peptide chains during problematic translation (PubMed:32099016, PubMed:32579943, PubMed:36302773). {ECO:0000250|UniProtKB:Q9QXN3, ECO:0000269|PubMed:10454579, ECO:0000269|PubMed:12077347, ECO:0000269|PubMed:25219498, ECO:0000269|PubMed:26924529, ECO:0000269|PubMed:32099016, ECO:0000269|PubMed:32579943, ECO:0000269|PubMed:36302773}. This is the function of ENSG00000103671 (TRIP4, thyroid hormone receptor interactor 4).