High impact information on Xic1

• Xic1 degradation is attenuated following completion of DNA replication [1].
• Furthermore, Xic1 destruction requires nuclear import, but not nuclear export, and requires the formation of a transport-competent nuclear envelope, but not interactions between the lamina and chromatin [2].
• This resulted in a Xic1 protein that was nevertheless degraded in a manner similar to wild-type Xic1, suggesting that phosphorylation of Xic1 is not critical for its nuclear ubiquitination or proteolysis [3].
• Further deletion analyses identified at least 3 lysine residues within the Xic1 C terminus that are targeted for specific ubiquitination [3].
• Using deletion mutagenesis, our studies indicated that the C-terminal 50 amino acids of Xic1 are critical for its proteolysis beyond a role in nuclear transport [3].

Biological context of Xic1

• Xic1 is targeted for degradation in interphase extracts in a manner dependent on both the ubiquitin conjugating enzyme, Cdc34, and nuclei [4].
• To address the role of phosphorylation on Xic1 turnover, all the potential phosphorylation sites within the C-terminal 50 amino acids of Xic1 were mutated to alanine to prevent possible phosphorylation [3].

References