Characterization of human hect domain family members and their interaction with UbcH5 and UbcH7.
The hect domain protein family was originally identified by sequence similarity of its members to the C-terminal region of E6-AP, an E3 ubiquitin-protein ligase. Since the C terminus of E6-AP mediates thioester complex formation with ubiquitin, a necessary intermediate step in E6-AP-dependent ubiquitination, it was proposed that members of the hect domain family in general have E3 activity. The hect domain is approximately 350 amino acids in length, and we show here that the hect domain of E6-AP is necessary and sufficient for ubiquitin thioester adduct formation. Furthermore, the human genome encodes at least 20 different hect domain proteins, and in further support of the hypothesis that hect domain proteins represent a family of E3s, several of these are shown to form thioester complexes with ubiquitin. In addition, some hect domain proteins interact preferentially with UbcH5, whereas others interact with UbcH7, indicating that human hect domain proteins can be grouped into at least two classes based on their E2 specificity. Since E3s are thought to play a major role in substrate recognition, the presence of a large family of E3s should contribute to ensure the specificity and selectivity of ubiquitin-dependent proteolytic pathways.
Schwarz
S E
SE
Deutsches Krebsforschungszentrum, Angewandte Tumorvirologie, Im Neuenheimer Feld 242, 69120 Heidelberg, Germany.
Rosa
J L
JL
Scheffner
M
M
D000595:Amino Acid Sequence; D056827:Endosomal Sorting Complexes Required for Transport; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008025:Ligases / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D014452:Ubiquitins / Q000378:metabolism
D056827:Endosomal Sorting Complexes Required for Transport; D005656:Fungal Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D016159:Tumor Suppressor Protein p53; D014452:Ubiquitins; C079437:UBE2L3 protein, human; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D044767:Ubiquitin-Protein Ligases; D008025:Ligases; C469287:RSP5 protein, S cerevisiae