PROTEIN TARGETING TO SUBNUCLEAR HIGHER-ORDER STRUCTURES - A NEW LEVELOF REGULATION AND COORDINATION OF NUCLEAR PROCESSES

Though there are no separating membranes within the nucleus, different factors are often concentrated at sites where their respective functi on is required, a phenomenum referred to as functional organization of the nucleus. How is then this organization achieved and how are the d ifferent metabolic processes integrated in the nucleus? One emerging p rinciple was revealed by the identification of protein domains that, t hough not involved in catalysis, regulate enzyme activity at a higher order level by targeting enzymes to the right place at the right time. These targeting sequences constitute an assembly code for nuclear 'pr otein factories,' which ensure the extremely high efficiency and accur acy needed in a complex and competitive environment as the living mamm alian cell. J. Cell. Biochem. 70:222-230, 1998. (C) 1998 Wiley-Liss, I nc.