title: High mobility group box 1 protein is methylated and transported to cytoplasm in clear cell renal cell carcinoma.
abstract: BACKGROUND
  The high mobility group box 1 (HMGB1) protein is a widespread nuclear protein present in most cell types. It typically locates in the nucleus and functions as a nuclear cofactor in transcription regulation. However, HMGB1 can also localize in the cytoplasm and be released into extracellular matrix, where it plays critical roles in carcinogenesis and inflammation. However, it remains elusive whether HMGB1 is relocated to cytoplasm in clear cell renal cell carcinoma (ccRCC).
  
  
  METHODS
  Nuclear and cytoplasmic proteins were extracted by different protocols from 20 ccRCC samples and corresponding adjacent renal tissues. Western blotting and immunohistochemistry were used to identify the expression of HMGB1 in ccRCC. To elucidate the potential mechanism of HMGB1 cytoplasmic translocation, HMGB1 proteins were enriched by immunoprecipitation and analyzed by mass spectrometry (MS).
  
  
  RESULTS
  The HMGB1 protein was overexpressed and partially localized in cytoplasm in ccRCC samples (12/20, 60%, p<0.05). Immunohistochemistry results indicated that ccRCC of high nuclear grade possess more HMGB1 relocation than those with low grade (p<0.05). Methylation of HMGB1 at lysine 112 in ccRCC was detected by MS. Bioinformatics analysis showed that post-translational modification might affect the binding ability to DNA and mediate its translocation.
  
  
  CONCLUSIONS
  Relocation of HMGB1 to cytoplasm was confirmed in ccRCC. Methylation of HMGB1 at lysine 112 might the redistribution of this cofactor protein.
authors.affiliation: Department of Urology, Provincial Hospital Affiliated to Shandong University, Jinan, China E-mail : kyoto2310@sina.com.
authors.forename: Fei
authors.initials: F
authors.lastname: Wu
authors.forename: Zuo-Hui
authors.initials: ZH
authors.lastname: Zhao
authors.forename: Sen-Tai
authors.initials: ST
authors.lastname: Ding
authors.forename: Hai-Hu
authors.initials: HH
authors.lastname: Wu
authors.forename: Jia-Ju
authors.initials: JJ
authors.lastname: Lu
mesh_terms: D002292:Carcinoma, Renal Cell / Q000235:genetics* / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism*; D024243:HMGB1 Protein / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D008745:Methylation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000235:genetics; D021381:Protein Transport / Q000502:physiology*
chemical_list: D024243:HMGB1 Protein; C585491:HMGB1 protein, human; D009687:Nuclear Proteins