This entry includes a group of E3 ubiquitin-protein ligases, including HECTD1/TRIP12 from humans, Ufd4 from budding yeasts and UPL3/4 from Arabidopsis. TRIP12 is involved in ubiquitin fusion degradation (UFD) pathway and regulation of DNA repair [, ]. HECTD1 regulates intracellular localization and secretion of Hsp90 and is essential for the correct development of the cranial neural folds and neural tube closure [, ].
This domain is found on the N-terminal region of peptidyl-prolyl cis-trans isomerase FKBP3 and in the core region of E3 ubiquitin ligase HectD1. It adopts a compact 5-helix bundle, hence termed BTHB (Basic Tilted Helix Bundle) domain. In FKBP3, it has been suggested to have a role in regulating the association state of nucleosomes by interacting with nucleolin. Moreover, this basic domain in FKBP35 forms alternative complexes with other chromatin-related proteins, such as the HDAC1, HDAC2, and the transcriptional regulator YY1, the DNA binding activity of which is enhanced on binding FKBP3. Structural analysis of this fold suggests that the DNA binding properties of FKBP3 and HectD1 are presented by the conserved basic region [].
