The Acidic Tail domain of Human Cdc34 is Required for p27Kip1 Ubiquitination and Complementation of a cdc34 Temperature Sensitive Yeast Strain

Abstract

Human Cdc34 is an ubiquitin conjugating enzyme or E2 that ubiquitinates substrates including p27 Kip1 , IκBα, Wee1 and MyoD. Cdc34 possesses a core catalytic domain encoding the active site cysteine and an acidic tail domain within the carboxyl terminal 36 amino acids. Studies suggest that Cdc34 is phosphorylated in mammalian cells at 5 potential residues within the tail domain. In order to study the biological significance of the Cdc34 acidic tail domain and the possible significance of phosphorylation within this region, we tested the ability of human Cdc34 mutants to complement the cdc34-2 temperature sensitive (ts) strain of Saccharomyces cerevisiae. Our studies indicated that complementation of the cdc34-2 ts strain was critically dependent upon the carboxylterminal 36 amino acids of human Cdc34, but did not require phosphorylation of human Cdc34 residues S203, S222, S231, T233, and S236. Further studies demonstrated that although a Cdc34 mutant bearing a deletion of the C-terminal 36 amino acids (Cdc34

The Human Cdc34 Carboxyl Terminus Contains a Non-covalent Ubiquitin Binding Activity That Contributes to SCF-dependent Ubiquitination

“…Previous studies have shown that the full-length hCdc34 but not its truncated form (hCdc34 ) is able to support growth in the temperaturesensitive cdc34-2 yeast strain at non-permissive temperature (37°C) when the endogenous Cdc34 is disabled (16). As shown (Fig.…”

“…5 The abbreviations used are: hCdc34, human Cdc34; Bistris propane, able to complement growth defects by a temperature-sensitive cdc34 mutant yeast strain (cdc34-2, harboring the G58R mutation) at non-permissive temperature (15,16 , respectively (5,16). Previous studies have shown that the yeast Cdc34 C-terminal tail is required for the G 1 -to-S phase transition of the cell cycle and that this activity is probably mediated by the ability of the yeast Cdc34 C terminus to interact with SCF (17,18).…”

Evidence that the Human Cytomegalovirus IE2-86 Protein Binds mdm2 and Facilitates mdm2 Degradation

“…The last 37 amino acids of IE2-86 have been shown to contain a transferable transactivation domain that is required for transactivation, autoregulation, and DNA binding (4,13,30). The acidic domains of other proteins were important for ubiquitination reactions (6,42), suggesting the possibility of a role for this region of IE2-86 in catalysis. An IE2-86-mdm2 complex might recruit another coactivator(s), corepressor(s), kinase(s), or component(s) responsible for protein degradation by synergy of its zinc finger/LIM and acidic domains.…”

The CK2 phosphorylation of catalytic domain of Cdc34 modulates its activity at the G1to S transition inSaccharomyces cerevisiae

“…20 Yeast Cdc34, human CDC34 and its homologous CDC34B are phosphorylated by CK2. [21][22][23][24][25][26] The CK2 phosphorylation sites of human CDC34 are localized within the C-terminal 36 amino acids (Ser203, Ser222, Ser231, Thr233, Ser236). 25,26 Similarly, yeast Cdc34 is phosphorylated by CK2 on the C-terminal tail (Ser207, Ser216, Ser282).…”