The object of the proposed investigation is to gain additional insights into the molecular events and regulatory mechanisms involved in the alterations of cell structure and function during the mammalian cell cycle. Synchronized HeLa S3 cells and an adeno-virus type 2 transformed rat embryo cell line will be employed in these investigations. Alterations in the structure and function of the nuclear envelope in the cell cycle will be investigated by asking specific questions concerning the synthesis, fate, and structural relationships of selective polypeptides of the inner nuclear membrane, as well as the membrane-associated Mg++-dependent Adenosine Triphosphatase (MgATPase). Details of the biochemical mechanisms involved in the regulation of gene expression during the cell cycle will be investigated by use of the virus-specific RNA of adeno-virus 2 transformed rat embryo cells as a model. The relationship between the control of the expression of the integrated viral genome and the cellular genome will be studied in synchronized cells and should increase our knowledge of the independence and dependence of the transforming viral genome on cellular functions.