Phosphorylation of Human Tristetraprolin in Response to Its Interaction with the CbI Interacting Protein CIN85
Abstract
Background: Tristetraprolin (TTP) is the prototype member of a family of CCCH tandem
zinc finger proteins and is considered to be an anti-inflammatory protein in mammals.
TTP plays a critical role in the decay of tumor necrosis factor alpha (TNF) mRNA,
among others, by binding AU-rich RNA elements in the 3'-untranslated regions of this
transcript and promoting its deadenylation and degradation. Methodology/Principal
Findings: We used yeast two-hybrid analysis to identify potential protein binding
partners for human TTP (hTTP). Various regions of hTTP recovered 31 proteins that
fell into 12 categories based on sequence similarities. Among these, the interactions
between hTTP and CIN85, cytoplasmic poly (A) binding protein (PABP), nucleolin and
heat shock protein 70 were confirmed by co-immunoprecipitation experiments. CIN85
and hTTP co-localized in the cytoplasm of cells as determined by confocal microscopy.
CIN85 contains three SH3 domains that specifically bind a unique proline-arginine
motif (PXXXPR) found in several CIN85 effectors. We found that the SH3 domains of
CIN85 bound to a PXXXPR motif located near the C-terminus of hTTP. Co-expression of
CIN85 with hTTP resulted in the increased phosphorylation of hTTP at serine residues
in positions 66 and 93, possibly due in part to the demonstrated association of mitogen-activated
protein kinase kinase kinase 4 (MEKK4) to both proteins. The presence of CIN85 did
not appear to alter hTTP's binding to RNA probes or its stimulated breakdown of TNF
mRNA. Conclusions/Significance: These studies describe interactions between hTTP and
nucleolin, cytoplasmic PABP, heat shock protein 70 and CIN85; these interactions were
initially discovered by two-hybrid analysis, and confirmed by coimmunoprecipitation.
We found that CIN85 binding to a C-terminal motif within hTTP led to the increased
phosphorylation of hTTP, possibly through enhanced association with MEKK4. The functional
consequences to each of the members of this putative complex remain to be determined.
Type
Other articleSubject
tumor-necrosis-factormessenger-rna decay
zinc-finger proteins
growth-factor receptors
map kinase pathway
au-rich elements
down-regulation
transcription factor
deficiency syndrome
signaling
pathway
biology
multidisciplinary sciences
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https://hdl.handle.net/10161/4530Published Version (Please cite this version)
10.1371/journal.pone.0009588Citation
Kedar,Vishram P.;Darby,Martyn K.;Williams,Jason G.;Blackshear,Perry J.. 2010. Phosphorylation
of Human Tristetraprolin in Response to Its Interaction with the CbI Interacting Protein
CIN85. Plos One 5(3): A213-A227.
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