Ataxin-3, the MJD1 gene product, interacts with the two human homologs of yeast DNA repair protein RAD23, HHR23A and HHR23B.
Machado-Joseph disease (MJD) is an autosomal dominant neurodegenerative disorder caused by an expansion of the polyglutamine tract near the C-terminus of the MJD1 gene product, ataxin-3. The mutant ataxin-3 forms intranuclear inclusions in cultured cells as well as in diseased human brain and also causes cell death in transfected cells. However, the normal function of ataxin-3 remains unknown. To explore the function of ataxin-3, we used the two-hybrid system to screen for the protein(s) that interacts with ataxin-3. We found that ataxin-3 interacts with two human homologs of the yeast DNA repair protein RAD23, HHR23A and HHR23B. Furthermore, we confirmed that ataxin-3 interacts with the -ubiquitin-like domain at the N-terminus of the HHR23 proteins, which is important for nucleotide excision repair; however, ataxin-3 does not interact with -ubiquitin, implying that ataxin-3 might be functionally associated with the HHR23 proteins through this specific interaction. The normal and mutant ataxin-3 proteins show no difference in their ability to bind to the HHR23 proteins. However, in 293 cells HHR23A is recruited to intranuclear inclusions formed by the mutant ataxin-3 through its interaction with ataxin-3. These results suggest that this interaction is associated with the normal function of ataxin-3 and that some functional abnormality of the HHR23 proteins might exist in MJD.
Wang
G
G
Laboratory for CAG Repeat Diseases, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan.
Sawai
N
N
Kotliarova
S
S
Kanazawa
I
I
Nukina
N
N
D000067699:Ataxin-3; D001665:Binding Sites; D002460:Cell Line; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D017827:Machado-Joseph Disease; D016296:Mutagenesis; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins; D011233:Precipitin Tests; D012097:Repressor Proteins; D020798:Two-Hybrid System Techniques; D014452:Ubiquitins / Q000378:metabolism
D004268:DNA-Binding Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C513287:RAD23B protein, human; D012097:Repressor Proteins; D014452:Ubiquitins; C086985:RAD23A protein, human; C092341:ATXN3 protein, human; D000067699:Ataxin-3; D045643:DNA Repair Enzymes