COMPLEX-FORMATION OF THE SPINACH CHLOROPLAST PSBA MESSENGER-RNA 5'-UNTRANSLATED REGION WITH PROTEINS IS DEPENDENT ON THE RNA STRUCTURE

RNA-protein interactions are part of many regulatory pathways in gene expression. In chloroplasts of higher plants and of green algae, gene regulation by posttranscriptional processes such as differential regul ation of mRNA stability and control of translation plays a major role during chloroplast development and light-dependent protein expression. Regulation here is mediated by interactions of RNA-binding proteins w ith the respective mRNAs. In this work, structural requirements for pr otein-RNA complex formation between the 5' untranslated region of the spinach psbA mRNA (encoding the D1 protein of photosystem II) and stro mal proteins are analyzed. For this, a combination of temperature grad ient gel electrophoresis and gel shift analysis is employed to study s everal variants of the psbA 5' untranslated region. Supported by theor etical interpretation of the data and analysis of the structures by ch emical probing, we show that a certain structure of the RNA is necessa ry for protein complex formation. Already very subtle structural chang es within the RNA interfere with binding and thereby with the biologic al activity of the mRNA.