E3 ubiquitin-protein ligase which triggers the ubiquitination and subsequent degradation of SGS3 in response to heat (PubMed:30778176). Involved in the mechanisms necessary for quick response to heat and subsequent heritable transgenerational memory of heat acclimation (global warming) such as early flowering and attenuated immunity; this process includes epigenetic regulation as well as post-transcriptional gene silencing (PTGS) (PubMed:30778176). In response to heat, HSFA2 is activated and promotes the expression of REF6 which in turn derepresses HSFA2, thus establishing an heritable feedback loop able to trigger SGIP1 and subsequent SGIP1-mediated SGS3 degradation; this prevents the biosynthesis of trans-acting siRNA (tasiRNA) and leads to the release of HTT5, which drives early flowering but attenuates immunity (PubMed:30778176). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein degradation; proteasomal ubiquitin-dependent pathway. Protein modification; protein ubiquitination. Interacts with SGS3 in cytoplasmic granules. Co-localizes with SGS3 in cytoplasmic granules. Up-regulated in heat-stressed plants and unstressed progeny in a HSFA2-dependent manner. Impaired heat-induced decrease of SGS3 levels and delayed SGS3 degradation associated with abolished heat-dependent early flowering and trans-acting siRNA (tasiRNA siR255 and siR1511) accumulation (PubMed:30778176). Lost heritable transgenerational thermomemory (PubMed:30778176).