Regulation of protease and protease inhibitor gene expression: the role of the 3'-UTR and lessons from the plasminogen activating system.
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3' Untranslated Regions↗
Biomedical subjects
Stan Stasinopoulos
Publications and source records attributed to Stan Stasinopoulos.
Inherent instability of plasminogen activator inhibitor type 2 mRNA is regulated by tristetraprolin.
Plasminogen activator inhibitor type 2 (PAI-2) is a serine protease inhibitor that is subject to regulation at the post-transcriptional level. At least two mRNA instability elements reside within the PAI-2 transcript; one in the coding region and another within the 3'-untranslated region (UTR). For the latter, a functional AU-rich motif (ARE) has been identified that provides a binding site for a number of cellular proteins, including the mRNA stability protein, HuR. In this study, we used the yeast three-hybrid system to screen a human leukocyte cDNA library to identify other proteins that associate with the PAI-2 ARE. This screen identified tristetraprolin (TTP) as a PAI-2 mRNA ARE-binding protein. UV cross-linking and immunoprecipitation experiments showed that TTP expressed in HEK293 cells could associate with the PAI-2 ARE in vitro. Co-transfection of plasmids expressing TTP and PAI-2 in HEK293 cells resulted in an increase in the decay rate of PAI-2 mRNA and loss of PAI-2 protein in a process that was dependent upon the PAI-2 3'-UTR. The 29-nt PAI-2 AU-rich element alone was also capable of conferring TTP-dependent mRNA instability to a reporter transcript. The extent of PAI-2 mRNA stability was remarkably sensitive to TTP since TTP-dependent PAI-2 mRNA decay occurred at TTP levels that were below Western blot detection limits. This study identifies TTP as a functional PAI-2 ARE-binding protein that modulates the post-transcriptional regulation of the PAI-2 gene.
3' Untranslated Regions↗
A mitochondrial specific stress response in mammalian cells.
Cells respond to a wide variety of stresses through the transcriptional activation of genes that harbour stress elements within their promoters. While many of these elements are shared by genes encoding proteins representative of all subcellular compartments, cells can also respond to stresses that are specific to individual organelles, such as the endoplasmic reticulum un folded protein response. Here we report on the discovery and characterization of a mitochondrial stress response in mammalian cells. We find that the accumulation of unfolded protein within the mitochondrial matrix results in the transcriptional upregulation of nuclear genes encoding mitochondrial stress proteins such as chaperonin 60, chaperonin 10, mtDnaJ and ClpP, but not those encoding stress proteins of the endoplasmic reticulum. Analysis of the chaperonin 60/10 bidirectional promoter identified a CHOP element as the mitochondrial stress response element. Dominant-negative mutant forms of CHOP and overexpression of CHOP revealed that this transcription factor, in association with C/EBPbeta, regulates expression of mitochondrial stress genes in response to the accumulation of unfolded proteins.
Adenosine Triphosphatases↗
Prothrombin G20210A is a bifunctional gene polymorphism.
The G20210A polymorphism has been shown to alter the efficiency of prothrombin mRNA processing. Here we show that the G20210A mutation also alters prothrombin mRNA stability. Three-fold more prothrombin protein and mRNA were produced in NIH-3T3 cells transfected with the prothrombin cDNAs containing the 20210A variant compared to cells expressing the 20210G variant. mRNA stability assays using chimeric globin transcripts harboring the G or A variant of the 97 nt prothrombin 3'-UTR indicated that the 20210G variant conferred greater instability to the globin reporter transcript than the A variant in transfected HepG2 cells. Both variants of the prothrombin 3'-UTR were shown to provide binding sites for a number of cellular proteins including HuR, an RNA binding protein associated with mRNA stability. Our results indicate that the G20210A is a bifunctional polymorphism, as it not only alters the efficiency of mRNA processing, but also the decay rate of prothrombin mRNA.
3' Untranslated Regions↗