Huntingtin Interacting Protein 2 (HIP2)

HIP2 belongs to the ubiquitin-conjugating enzyme family. It binds selectively to a large region at the N terminus of huntingtin. This interaction is not influenced by the length of the huntingtin polyglutamine tract. This protein has been implicated in the degradation of huntingtin and suppression of apoptosis.

The 200-amino acid HIP2 protein sequence was identical to that of bovine ubiquitin-conjugating enzyme E2-25K. Assays of the interaction of HIP2 with huntingtin revealed that HIP2 binds selectively to a large region at the N terminus of huntingtin. This interaction is not influenced by the length of the huntingtin polyglutamine tract. Western blot analysis detected protein bands of 25, 28, and 45 kD; the 28-kD band appeared to be selective for tissues of the central nervous system.