The polyamines putrescine, spermidine, and spermine are major cellular components of all living cells and have been shown to be involved in many systems related to growth and differentiation. Our current and older studies have been directed at learning how these polyamines are synthesized and regulated and their physiological function in vivo. As part of these studies we are currently concentrating on the biochemistry, regulation, ad genetics of these amines in Saccharomyces cerevisiae. In our past studies, we prepared mutants in the biosynthetic pathways and showed that cells that were deprived of spermidine or spermine were unable to grow, to sporulate, or to maintain the virus-like RNA killer plasmids of yeast. Our current studies have demonstrated three additional in vivo functions: (1) Spermidine protects yeast from oxidative damage due to superoxide formation. (2) Spermidine is necessary for the survival of mitochondria, which are lost in amine- deficient cells even in air. (3) We have also shown an unusual and unexpected effect of spermidine on protein synthesis in vivo. With the use of a model system for the study of ribosomal frameshifting, described by Wickner and Dinman, and in collaboration with them, we have shown that polyamines are essential for the maintenance of the correct translational efficiency of +1 ribosomal frameshifting. Ribosomal frameshifting is of particular importance in the development of retroviruses and -1 ribosomal frameshifting is known to be important in the """"""""gag-pol"""""""" type of protein synthesis in the L-A dsRNA system of yeast studied by Dinman and Wickner and in the Ty transposon system. In very recent studies we have shown that the amount of ribosomal frameshifting is controlled by the putrescine/spermidine ratio, i.e. not by spermidine alone. Other studies have been concerned with further studies on the enzymes involved in the biosynthetic pathway and their regulation.
