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Tripartite motif-containing protein 32 is a protein that in humans is encoded by the TRIM32 gene.[1][2][3][4] Since its discovery in 1995, TRIM32 has been shown to be implicated in a number of diverse biological pathways.


The protein encoded by this gene is a member of the tripartite motif (TRIM) family. The TRIM motif includes three zinc-binding domains, a RING, a B-box type 1 and a B-box type 2, and a coiled-coil region.[4]

Subcellular distribution

The protein localizes to cytoplasmic bodies. The protein has also been localized to the nucleus, where it interacts with the activation domain of the HIV-1 Tat protein. The Tat protein activates transcription of HIV-1 genes.[4]


TRIM32 has been shown to interact with:



Currently, TRIM32 is believed to employ two different mechanisms to affect molecular targets. First, it can act through its N-terminal RING finger as an E3 ubiquitin ligase, responsible for attaching ubiquitin molecules to lysine residues of target proteins, in order to mark them for proteosome degradation. Currently evidence suggests TRIM32 ubiquitinates multiple proteins including c-Myc, dysbindin, actin, piasy, and Abl-interactor2 (ABI2). The second mechanism by which TRIM32 is believed to operate involves binding of proteins to the C-terminal NHL repeat, which has been shown to activate miRNAs.[7]


Research has recently shown the importance of TRIM32 in the development of the mouse neocortex. In the mouse neocortex, neural progenitor cells generate daughter cells which either differentiate into specific neurons or maintain the progenitor state of the mother cell. TRIM32 helps control the balance between differentiating and progenitor cells by localizing to a pole during progenitor cell division, and thus becoming concentrated in one of the two daughter cells. This asymmetric division of TRIM32 induces neuronal differentiation in daughter cells which contain high TRIM32 concentrations, while cells with low TRIM32 concentrations retain progenitor cell fate. Proposed theories on how TRIM32 induces differentiation involve the ubiquitination of the transcription factor c-Myc and the binding of Argonaute-1 (Ago-1). The binding of Ago-1 induces activity of miRNAs, particularly Let-7a, which has been shown to play a role in regulating proliferation and neuronal differentiation.[7]

Skeletal muscle

TRIM32 is expressed in skeletal muscle, where it interacts with myosin and may ubiquitinate actin (it has been shown to do so in vitro).[5] No difference has been observed between wild-type and LHMD2H-mutated TRIM32 in terms of actin or myosin binding, however, and thus the mechanism which causes the muscular dystrophy, LGMD2H, is still unknown.[10] Additionally, TRIM32 is known to ubiquitinate dysbindin, a protein associated with both skeletal muscles and neural tissue. The purpose and effects of the ubiquitination of dysbindin are as yet unclear.[8]

Clinical significance

Mutation-associated diseases

Bardet–Biedl syndrome (BBS): TRIM32 is one of 14[11] genes known to be linked with BBS. Specifically a mutation (P130S) in the B-box of TRIM32 gives rise to BBS.[8]

Limb-girdle muscular dystrophy type2H (LGMD2H): LGMD2H is caused by 4 mutations of TRIM32 in the C-terminal NHL domain: D487N (third NHL repeat), R394H (first NHL repeat), T520TfsX13 (fourth NHL repeat), and D588del (fifth NHL repeat).[8]


TRIM32 is overexpressed in skin cancer cells. It is thought that TRIM32 regulates NF-κB activity through ubiquitination of Protein Inhibitor of Activated STAT Y (Piasy).[9] Piasy acts as an inhibitor of NF-κB, and NF-κB acts as an anti-apoptotic factor. Thus, when Piasy is present, NF-κB is inhibited, and keratinocytes undergo apoptosis when exposed to ultraviolet-B radiation or TNFα, preventing cancer formation. When TRIM32 is overexpressed, Piasy is degraded, allowing NF-κB to function, and thus when cells are exposed to ultraviolet-B radiation or TNFα, apoptosis does not occur, potentially allowing cancer formation.[10]

TRIM32 additionally promotes cancer formation by ubiquitinating Abl-interactor 2 (Abi2), which is a tumor suppressor and inhibitor of cell migration.[9]

See also


  1. Reymond A, Meroni G, Fantozzi A, Merla G, Cairo S, Luzi L, Riganelli D, Zanaria E, Messali S, Cainarca S, Guffanti A, Minucci S, Pelicci PG, Ballabio A (May 2001). "The tripartite motif family identifies cell compartments". EMBO J. 20 (9): 2140–51. doi:10.1093/emboj/20.9.2140. PMC 125245. PMID 11331580.
  2. Fridell RA, Harding LS, Bogerd HP, Cullen BR (Jul 1995). "Identification of a novel human zinc finger protein that specifically interacts with the activation domain of lentiviral Tat proteins". Virology. 209 (2): 347–57. doi:10.1006/viro.1995.1266. PMID 7778269.
  3. Chiang AP, Beck JS, Yen HJ, Tayeh MK, Scheetz TE, Swiderski RE, Nishimura DY, Braun TA, Kim KY, Huang J, Elbedour K, Carmi R, Slusarski DC, Casavant TL, Stone EM, Sheffield VC (Apr 2006). "Homozygosity mapping with SNP arrays identifies TRIM32, an E3 ubiquitin ligase, as a Bardet-Biedl syndrome gene (BBS11)". Proc Natl Acad Sci U S A. 103 (16): 6287–92. doi:10.1073/pnas.0600158103. PMC 1458870. PMID 16606853.
  4. 4.0 4.1 4.2 "Entrez Gene: TRIM32 tripartite motif-containing 32".
  5. 5.0 5.1 Kudryashova E, Kudryashov D, Kramerova I, Spencer MJ (Nov 2005). "Trim32 is a ubiquitin ligase mutated in limb girdle muscular dystrophy type 2H that binds to skeletal muscle myosin and ubiquitinates actin". J Mol Biol. 354 (2): 413–24. doi:10.1016/j.jmb.2005.09.068. PMID 16243356.
  6. Kano S, Miyajima N, Fukuda S, Hatakeyama S (July 2008). "Tripartite motif protein 32 facilitates cell growth and migration via degradation of Abl-interactor 2". Cancer Res. 68 (14): 5572–80. doi:10.1158/0008-5472.CAN-07-6231. PMID 18632609.
  7. 7.0 7.1 7.2 Schwamborn J, Berezikov E, Knoblich J (March 2009). "The TRIM-NHL protein TRIM32 activates microRNAs and prevents self-renewal in mouse neural progenitors". Cell. 136 (5): 913–925. doi:10.1016/j.cell.2008.12.024. PMC 2988196. PMID 19269368.
  8. 8.0 8.1 8.2 8.3 Locke M, Tinsley CL, Benson MA, Blake DJ (Apr 2009). "TRIM32 is an E3 ubiquitin ligase for dysbindin". Hum Mol Genet. 18 (13): 2344–58. doi:10.1093/hmg/ddp167. PMC 2694686. PMID 19349376.
  9. 9.0 9.1 9.2 Kudryashova E, Wu J, Havton LA, Spencer MJ (Apr 2009). "Deficiency of the E3 ubiquitin ligase TRIM32 in mice leads to a myopathy with a neurogenic component". Hum Mol Genet. 18 (7): 1353–67. doi:10.1093/hmg/ddp036. PMC 2722196. PMID 19155210.
  10. 10.0 10.1 Albor A, El-Hizawi S, Horn EJ, Laederich M, Frosk P, Wrogemann K, Kulesz-Martin M (Jun 2006). "The interaction of Piasy with Trim32, an E3-ubiquitin ligase mutated in limb-girdle muscular dystrophy type 2H, promotes Piasy degradation and regulates UVB-induced keratinocyte apoptosis through NFkappaB". J Biol Chem. 281 (35): 25850–66. doi:10.1074/jbc.M601655200. PMID 16816390.
  11. Hamosh, Ada (2012-11-02). "OMIM entry #209900 Bardet-Biedl Syndrome; BBS". Online Mendelian Inheritance in Man. McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine. Retrieved 2013-09-04.

External links

Further reading