A novel cytoplasmic GTPase XAB1 interacts with DNA repair protein XPA.
The xeroderma pigmentosum group A protein (XPA) plays a central role in nucleotide excision repair (NER). To identify proteins that bind to XPA, we screened a HeLa cDNA library using the yeast two-hybrid system. Here we report a novel cytoplasmic GTP-binding protein, designated XPA binding protein 1 (XAB1). The deduced amino acid sequence of XAB1 consisted of 374 residues with a molecular weight of 41 kDa and an isoelectric point of 4.65. Sequence analysis revealed that XAB1 has four sequence motifs G1-G4 of the GTP-binding protein family in the N-terminal half. XAB1 also contains an acidic region in the C-terminal portion. Northern blot analysis showed that XAB1 mRNA is expressed ubiquitously, and immunofluorescence analysis revealed that XAB1 is localized mainly in the cytoplasm. Consistent with the GTP-binding motif, purified recombinant XAB1 protein has intrinsic GTPase activity. Using the yeast two-hybrid system, we elucidated that XAB1 binds to the N-terminal region of XPA. The deletion of five amino acids, residues 30-34 of XPA, required for nuclear localization of XPA abolished the interaction with XAB1. These results suggest that XAB1 is a novel cytoplasmic GTPase involved in nuclear localization of XPA.
Nitta
M
M
Institute for Molecular and Cellular Biology, Osaka University, 1-3 Yamadaoka, Suita, Osaka 565-0871, Japan.
Saijo
M
M
Kodo
N
N
Matsuda
T
T
Nakatsu
Y
Y
Tamai
H
H
Tanaka
K
K
D000251:Adenosine Triphosphatases / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D003593:Cytoplasm / Q000201:enzymology*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D020558:GTP Phosphohydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009928:Organ Specificity; D011485:Protein Binding; D021381:Protein Transport; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D016415:Sequence Alignment; D017384:Sequence Deletion / Q000235:genetics; D013737:Testis / Q000378:metabolism; D020798:Two-Hybrid System Techniques; D014983:Xeroderma Pigmentosum / Q000235:genetics / Q000378:metabolism; D051760:Xeroderma Pigmentosum Group A Protein
D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C497314:XPA protein, human; D051760:Xeroderma Pigmentosum Group A Protein; D000251:Adenosine Triphosphatases; D020558:GTP Phosphohydrolases