MRNA transcript levels

Another important set of multiplexed assays monitor mRNA transcript levels. The expression level of all the genes involved in a known signal transduction pathway or other selective genes can be monitored simultaneously as a way of following compound effects on a cell. The current technologies for multiple mRNA detection include quantitative reverse transcriptional PCR (qRT-PCR), qNPA (quantitative nuclease protection assays), mass array assay technologies and branched DNA detection on Luminex beads (Panomics). The applications of such multiplexed in vitro and cell-based detection systems should provide more predicative information in hit finding and lead characterisation. 

The VDE mRNA transcript level was analyzed in market romaine lettuce by northern hybridization. The younger leaf tissues (yellow leaves and rapidly expanding green leaves) had low levels of transcript... 

Other useful sites for yeast genome analysis include Saccharomyces cerevisiae Promoter Database, listing known regulatory elements and transcriptional factors in yeast TRansposon-Insertion Phenotypes, Localization, and Expression in Saccharomyces (TRIPLES) database, which tracks the expression of transposon-induced mutants and the cellular localization of transposon-tagged proteins, and the Saccharomyces Cell Cycle Expression Database, presenting the first results on changes in mRNA transcript levels dming the yeast cell cycle. 

Clinical Investigations Diesel exhaust (mass median diameter <10 pm) at 300 pg/m associated with concentrations of NOj of 1.6 ppm, NO of 4.5 ppm for 1 h, CO of 7.5 ppm, total hydrocarbons of 4.3 ppm, formaldehyde of 0.26 mg/m and 4.3 x 10 suspended particles/ml in healthy human volunteers exposed for 1 h induced a 240 % median relative increase in interleukin-8 mRNA gene transcripts in the cells contained in bronchial lavage performed 6 h later (Salvi et al. 2000). There were no changes in the mRNA transcript levels for ILL-ip, ILL-4, TNF-a, interferon-y, and granulocyte-macrophage colony-stimulating factor after exposure to diesel exhaust compared with air. 

With respect to tissue distribution, the available data is limited to mRNA transcripts which, for all TAARs studied so far, are present at generally low levels when compared to e.g., 5-HT and DA receptors. The most... 

The entire population of mRNA transcripts in the cell, weighted by their expression levels. 

We can conclude that our results are compatible with a model for the control of PG synthesis at transcriptional level in response to the inducer but with certain levels of protein, apparently similar to that showing PG activity, and its corresponding mRNA in non-inducing conditions. Further studies in order to quantify the relative amount of these basal levels are on a course. 

Jaffe, H.A., Buhl, R., Borok, Z., Trapnell, B. and Crystal, R.G. (1989). Activated alveolar macrophages express increased levels of cytochrome b245 heavy chain mRNA transcripts correlating with enhanced capacity to release oxidants. Clin. Res. 37, 477A. 

Expression profiles at the protein level may throw more light on function, than those at the transcript level, as mRNA levels do not necessarily correlate with protein levels.7... 

Chloroplast protein synthesis is controlled largely at the post-transcriptional level [20,21] and can be repressed by the inclusion of antibiotics such as streptomycin in the sprouting medium. Streptomycin binds to the 16S rRNA and causes the ribosome to misread the mRNA sequence, producing incorrect and non-functional proteins [22]. 

Increased transcription levels are assumed to result in increased protein synthesis. One approach to reach this goal is to raise the transgene copy number by the use of amplification-promoting sequences derived from a spacer sequence of tobacco ribo-somal DNA [95]. Posttranscriptional processes such as capping, splicing and polya-denylation are important for high protein yields, and it is also important to maximize mRNA stability [84]. 

Regulation of expression may occur at both the transcriptional and post-transcriptional levels. The mRNA for GM-CSF contains (in common with those of some other cytokines) conserved regulatory sequences in the 3 untranslated region, which may affect its rate of translation. The gene is constitutively transcribed in monocytes, endothelial cells and fibroblasts, but the mRNA is unstable and so does not accumulate to levels sufficient to allow translation into significant amounts of protein. Activation of these cells results in the increased expression of GM-CSF protein, which arises from both an enhanced rate of transcription (as detected in nuclear runoff experiments) and also an increased stability of the mRNA, perhaps by mechanisms analogous to those described above during activation of G-CSF expression ( 2.2.3.1). 

Also, as with many biologically important membrane molecules, the expression of the soluble isoform is also tightly regulated at the level of mRNA transcripts. Consequently, either overproduction or imbalance in density of Fas isoforms is likely to play an important role in the control of Fas-mediated apoptosis in vivo. 

The transport from nucleus to cytoplasm is accompanied by modification at the 5 - and 3 -end of the pre-RNA, as well as by processing (splicing) of the primary transcript. The 3 -end modifications and sphcing decide which information contained in the primary transcript is made available for protein biosynthesis. The information content of the processed mRNA can be specifically influenced by these processes. This has an important impact on the tissue- and cell-specific protein expression. 3 -modification and splicing are tightly coupled to extranuclear transport. Interventions in the transport process are another possibihty for a regulation at the post-transcriptional level. 

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