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Ubiquitination of HEXIM1 by HDM2
Author(s) -
Chao ShengHao,
Lau Joanne,
Diribarne Gaelle,
Dey Anwesha,
Bensaude Olivier,
Lane David P
Publication year - 2009
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.23.1_supplement.848.3
Subject(s) - transactivation , p tefb , chemistry , ubiquitin ligase , rna polymerase ii , transcription factor , microbiology and biotechnology , ubiquitin , proteasome , biology , biochemistry , gene expression , gene , promoter
Hexamethylene bis‐acetamide inducible protein 1 (HEXIM1) is an inhibitor of positive transcription elongation factor b (P‐TEFb), which controls RNA polymerase II transcription and human immunodeficiency virus Tat transactivation. In cells, more than half of P‐TEFb is associated with HEXIM1 resulting in the inactivation of P‐TEFb. Recently, we found that nucleophosmin (NPM), a key factor involved in p53 signaling pathway, interacts with HEXIM1 and activates P‐TEFb‐dependent transcription. Here we report that HDM2, another important regulator of p53, ubiquitylates HEXIM1 specifically. We also identify the lysine residues, which are located with the basic region of HEXIM1, required for ubiquityl modification. Interestingly, the HDM2‐induced HEXIM1 ubiquitination does not lead to proteasome‐mediated protein degradation. Our results demonstrate that HDM2 functions as a specific E3 ubiquitin ligase for HEXIM1, suggesting a possible role for HEXIM1 in the regulation of p53 signaling pathway.