MULTIPLE MOLECULAR-LEVELS OF CELL-CYCLE REGULATION

The objective of this brief review is to stress the importance of mult iple levels of molecular regulation of complex processes such as cell growth and to illustrate their derangements as they occur in cancer ce lls. One major research emphasis today is the regulation of transcript ion by binding of transactivating proteins to promoter motifs. Another focus is on the multiple roles of protein phosphorylations in signal transduction pathways. Evidence is strong, however, that major control s exist at numerous other molecular levels as well (Fig. 1). These inc lude pre-mRNA processing, pre-mRNA degradation, mRNA degradation, cont rol of translation, permanent protein modifications, protein degradati on, reversible covalent protein alterations, noncovalent interactions with small molecules and with other proteins, and effects of relocatio ns into cell compartments. These controls are exhibited in all biologi cal processes. A few illustrative examples are briefly discussed, whic h come mainly from our researches in the area of cell cycle regulation and its derangement in cancer. (C) 1994 Wiley-Liss, Inc.