Studies performed under the frame of this research programme, have contributed to the explanation of some basic events in the function of cell cycle of Saccharomyces cerevisiae. The roles and interactions of some proteins involved and in the biological system connected to the protein Cdc6 were explained. Cdc6 represents one of the key regulatory proteins in initiation of DNA duplication as well as in segregation of chromosomes. Research on Saccharomyces cerevisiae cell cycle has a broader impact since this simple yeast system, which is relatively easy to investigate represents a good model for higher eukaryotic organisms. Our studies also contributed to the knowledge about post-translational processing in yeasts and fungi, representing important alternative systems for biosynthesis of various heterologous proteins. Furthermore, studies of early events in interaction between tumour necrosis factor alpha (TNF) and its receptors as well as research on structure - function relationship using numerous TNF analogues, contributed to the knowledge about functioning of this biologically and pharmaceutically very important protein.