Related Experiment Videos
Amyloid precursor protein mRNA stability is controlled by a 29-base element in the 3'-untranslated region
1Department of Pathology and Laboratory Medicine, University of Wisconsin, Madison 53792-2472.
Abstract:
In the accompanying paper (Zaidi, S. H. E., Denman, R., and Malter, J. S. (1994) J. Biol. Chem. 269, 24000-24006) we demonstrate that in tumor and normal cells, multiple cytosolic proteins interact with a 29-base sequence in the 3'-untranslated region of amyloid precursor protein (APP) mRNA. These data suggested that APP gene expression may be modulated by regulated APP mRNA decay. We have investigated this prediction by measuring the decay rates of APP mRNA in resting and mitogen-treated peripheral blood mononuclear cells and H4 and K562 tumor cell lines. In resting peripheral blood mononuclear cells, APP mRNA decayed with a half-life of 4 h. Under these conditions, the activity of APP mRNA-binding proteins was not detectable. After activation, binding protein activities were induced, and APP mRNA decay was blocked with a half-life of > 12 h. In log phase neuronal or lymphoid tumor cell lines, binding activity was constitutively present and APP mRNA displayed a half-life of > 12 h. Protein synthesis inhibition by cycloheximide had no effect on APP mRNA decay in normal or tumor cells. Transfected wild type or mutant APP mRNAs that lacked the 29-base region were stable (t1/2 > 10 h) in K562 tumor cells. Therefore, we conclude that the 29-base region functions in cis to destabilize APP mRNA in resting, normal cells. Upon activation APP mRNA-binding proteins are induced, interact with the 29-base region, and likely participate in stabilization of the mRNA.
Insights
Amyloid precursor protein (APP) mRNA decay is regulated by specific binding proteins. These proteins stabilize APP mRNA in activated cells and tumor cells, but not in resting normal cells.
Area of Science:
- Molecular Biology
- Gene Regulation
- Cell Biology
Background:
- Previous research indicated that cytosolic proteins bind to a specific 29-base sequence in the 3'-untranslated region of amyloid precursor protein (APP) mRNA.
- This interaction suggested that APP gene expression might be controlled through regulated decay of APP mRNA.
Purpose of the Study:
- To investigate the prediction that APP gene expression is modulated by regulated APP mRNA decay.
- To measure the decay rates of APP mRNA in various cell types under different conditions.
Main Methods:
- Measurement of APP mRNA decay rates in resting and mitogen-treated peripheral blood mononuclear cells.
- Analysis of APP mRNA decay in H4 and K562 tumor cell lines.
- Assessment of APP mRNA-binding protein activity and the effect of protein synthesis inhibition.
Main Results:
- In resting peripheral blood mononuclear cells, APP mRNA had a short half-life (4 h) with undetectable binding protein activity.
- Upon activation, binding protein activities were induced, leading to stabilization of APP mRNA (half-life > 12 h).
- Tumor cell lines exhibited constitutive binding activity and stable APP mRNA (half-life > 12 h).
- APP mRNA lacking the 29-base region was stable in tumor cells, indicating the region's role in destabilization.
Conclusions:
- The 29-base sequence in APP mRNA functions in cis to destabilize the mRNA in resting normal cells.
- Induced APP mRNA-binding proteins stabilize APP mRNA upon cellular activation.
- This mechanism highlights a novel regulatory pathway for APP gene expression.