Translational Control Involving A Novel Cytoplasmic RNA and Ribonucleoprotein

Abstract

Publisher Summary To investigate the role of cellular regulatory mechanisms involving inhibitory RNA (iRNA) and 10-S ribonucleoproteins (iRNP), this chapter presents a detailed study on the characterization and mechanism of action of these macromolecules. It also outlines recent progress made in this area. The results presented in the chapter strongly imply that iRNA and iRNP are genuine cytoplasmic macromolecular entities involved in the modulation of mRNA translation in a subtle manner at a post-transcriptional level. The iRNA and iRNP are quite distinct from the various eukaryotic RNA species that have modulating effects on in vitro translation systems. The potent inhibitory effect of iRNA and iRNP on mRNA translation is not exerted in an absolutely discriminatory manner. Rather, they act as specific inhibitors of mRNA binding to 43-S complex. This mode of inhibition distinguishes iRNA and iRNP from other cellular inhibitors that act through the phosphorylation of the eIF2 a-subunit. Because iRNA inhibits mRNA binding to ribosomes, it is quite likely that the relative affinities of mRNA and iRNA for this rate-limiting step in polypeptide synthesis may function as a subtle parameter in the cytoplasmic regulation of translation. Thus, a quantitative modulation of the translation of various mRNAs by iRNA rather than a specific discriminatory effect can lead to striking effects on cellular translation patterns.