E3 ubiquitin-protein ligase involved in Golgi membrane fusion and regulation of small GTPases (PubMed:15254018, PubMed:21988917, PubMed:22036506, PubMed:37537642, PubMed:38332367). Acts as a regulator of Golgi membrane dynamics during the cell cycle: recruited to Golgi membrane by Rab proteins and regulates postmitotic Golgi membrane fusion (PubMed:21988917). Acts by mediating ubiquitination during mitotic Golgi disassembly, ubiquitination serving as a signal for Golgi reassembly later, after cell division (PubMed:21988917). Specifically binds GTP-bound RAC1, mediating ubiquitination and subsequent degradation of active RAC1, thereby playing a role in host defense against pathogens (PubMed:22036506, PubMed:37537642, PubMed:38332367). May also act as a transcription regulator via its interaction with RARB (By similarity). {ECO:0000250|UniProtKB:Q3U0D9, ECO:0000269|PubMed:15254018, ECO:0000269|PubMed:21988917, ECO:0000269|PubMed:22036506, ECO:0000269|PubMed:37537642, ECO:0000269|PubMed:38332367}. This is the function of HACE1 (HECT domain and ankyrin repeat containing E3 ubiquitin protein ligase 1, Ensembl gene identifier ENSG00000085382).