SIVA ubiquitination and/or degradation-related activity and modulators thereof

A method for identifying a polypeptide that comprises a B-box-like ring with the amino acid sequence of SEQ ID NO:6, wherein said SEQ ID NO:6 has eight Cysteines and no Histidine, or a homolog thereof, said homolog comprising a B-box-like ring finger motif with eight cysteines, and no histidine, and an amino acid sequence that is at least 80% identical to that set forth in SEQ ID NO:6 and wherein said polypeptide is capable of self-ubiquitination, the method comprising:

• (i) contacting polypeptides comprising an ubiquitin, an El ubiquitin-activating enzyme, an E2 ubiquitin conjugating enzyme, and the polypeptide comprising said B-box-like ring with the amino acid sequence of SEQ ID NO:6 or homolog thereof;
• and
• (ii) measuring linkage of ubiquitin to said polypeptide comprising said B-box-like ring with the amino acid sequence of SEQ ID NO:6 or homoloq thereof,
• wherein the measurement of ubiquitin linked to said polypeptide comprising said B-box-like ring identifies said polypeptide as a polypeptide comprising said B-box-like ring capable of self-ubiquitination.