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TRIM5α as an E3 ubiquitin ligase
Author(s) -
Tanaka Makoto,
Yamauchi Keiko,
Kamitani Tetsu
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.848.11
Subject(s) - ubiquitin ligase , ubiquitin , ubiquitin protein ligases , dna ligase , hek 293 cells , proteasome , ring finger , microbiology and biotechnology , biology , in vitro , chemistry , enzyme , biochemistry , genetics , cell culture , gene
Human immunodeficiency virus type1 (HIV‐1) efficiently infects susceptible cells and causes acquired immunodeficiency syndrome (AIDS) in humans. Although HIV can also enter the cells of Old World monkeys, it encounters a block before reverse transcription. Data have shown that this species‐specific restriction is mediated at the post‐entry stage by a RING‐finger protein TRIM5α. The function of TRIM5α, however, is unknown. Since many RING‐finger proteins, such as TRIM21 (Ro52), have been identified as E3 ubiquitin ligases, we hypothesized that TRIM5α functions as an E3 ubiquitin ligase. To test this possibility, we examined the E3 ligase activity of TRIM5α in vitro. Its enzymatic activity was also tested by overexpressing TRIM5α in human embryonic kidney 293T cells. Our results indicated that TRIM5α ubiquitinates itself (self‐ubiquitination) in cooperation with the E2 ubiquitin‐conjugating enzyme UbcH5B; this showed that TRIM5α is a RING‐finger‐type E3 ubiquitin ligase. Interestingly, in HEK293T cells, TRIM5α was clearly conjugated with a monoubiquitin, as well as polyubiquitin chain, which does not target to the proteasome for degradation. Thus, we identified TRIM5α as an E3 ubiquitin ligase.