The proposed work consists of project I and II. Project I seeks to understand the structural and functional relationship of the multipartite viral RNAs. Our discovery of internal poly-A of about 25 nucleotides has shed new light of the "silent cistron" in a dicistronic setting, and the production of the subgenomic coat protein cistron from RNA3. Further research is in progress to determine the universality of internal poly-A in viral RNA messengers. Project II deals with synthesis of some mod@fied purines nucleosides and nucleotides. The objective is to relate structural changes to biological function. Work is still in progress in this area.