Posttranscriptional events

Between 10% and 20% of expressed genes in a cell are regulated by glucocorticoids. The number and affinity of receptors for the hormone, the complement of transcription factors and coregulators, and posttranscription events determine the relative specificity of these hormones actions in various cells. The effects of glucocorticoids are mainly due to proteins synthesized from mRNA transcribed... 

Schumm and Webb23 suggested that cyclic nucleotides can exert an influence on the posttranscriptional events of RNA processing and transport since they found that the addition of cyclic AMP or GMP stimulated the release of RNA from isolated hepatic nuclei. Subsequently, in preliminary experiments, the addition of cAMP to the cell-free system composed of cell saps of livers of control rats, but not composed of cell saps of livers of tryptophan-treated rats, caused increases in the release of labeled RNA from the liver nuclei of control rats. This response in the cell-free system to added cAMP probably reflects the in vivo concentrations of cAMP in the tissues from which the cytosol was prepared. Thus, these preliminary findings suggest that tryptophan may elevate in vivo the cAMP levels in liver cytosol, and this may be of importance in the enhanced nucleocytoplasmic translocation of mRNA in liver owing to tryptophan. However, preliminary assays of cAMP activities in the livers of control and tryptophan-treated rats have failed to reveal significant differences. 

In contrast to the subunits that form the various types of LDH, those of aldolase are coded for by a single gene therefore, the conversion of a to jS is a posttranscriptional event involving the deamination of a single asparagine residue in the a-subunits. 

Several biochemical events occur posttranscriptionally that define the response of cells to stimuli. For instance, alternative splicing, posttrans-lational modifications, regulation of enzyme activities, distribution of metabolites between cellular compartments, necessitate analysis at the level of the proteome and the metabolome. 

In conclusion, a number of events are related to non-antioxidant properties of a-tocopherol (Table 2), both at transcriptional and posttranscriptional level. However, whether a-tocopherol acts by a pleiotropic mechanism, or it binds to a receptor capable of regulating different reactions, still remains unknown. 

The events in posttranscriptional processing of mRNA are controlled by the phosphorylation state of the carboxy-terminal domain (CTD), part of RNA polymerase II. 

TNF-a converting enzyme (TACE) is a newly discovered enzyme in the disintegrin and metalloproteinase (ADAM) family (78). This enzyme releases the 17-kD mature TNF-a fiom membrane-bound TNF-a by cleaving Ala 76 and Val 77 linkage. TACE has also been shown to be involved with other cell surface protein shedding events such as the p55 and p75 TNF-a receptors (79). Our laboratory has previously shown that acute administration of alcohol (EtOH)to rats suppresses TNF-a production posttranscriptionally in the lung and blood (20,80). Recently, we have further defined the mechanism of TNF-a inhibition by EtOH, which revealed... 

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