title: Hepatitis B virus X protein interacts with a probable cellular DNA repair protein.
abstract: The mechanism of action of hepatitis B virus (HBV) X protein in transcriptional transactivation and in tumorigenesis remains obscure. We have used the yeast two-hybrid system to identify a cellular protein that can interact with HBV X protein. This protein, designated X-associated protein 1 (XAP-1), is a human homolog of the UV-damaged DNA-binding protein (UV-DDB) recovered from a monkey cell cDNA library. UV-DDB is presumed to be involved in DNA repair. The interaction between X protein and XAP-1 protein was verified by immunoprecipitation of yeast cell lysates expressing both proteins and by in vitro mixing with X protein expressed as a glutathione S-transferase fusion protein and XAP-1 protein either in HeLa cell extracts or synthesized by in vitro translation. We speculate that the interaction of X protein with a DNA repair protein may recruit cellular proteins to repair the partially double-stranded HBV genome or may modify cellular transcription processes. An effect on the cellular DNA repair system may explain a cofactor role for HBV in liver cancer development.
authors: Division of Molecular Virology, Baylor College of Medicine, Houston, Texas 77030.
authors: T H
authors: TH
authors: Lee
authors: S J
authors: SJ
authors: Elledge
authors: J S
authors: JS
authors: Butel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008113:Liver Neoplasms / Q000209:etiology; D008969:Molecular Sequence Data; D011817:Rabbits; D015534:Trans-Activators / Q000378:metabolism*; D054334:Viral Regulatory and Accessory Proteins; D015003:Yeasts / Q000378:metabolism
chemical_list: C091435:DDB1 protein, human; D004268:DNA-Binding Proteins; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein