INVERTED REPEATS, STEM-LOOPS, AND CRUCIFORMS - SIGNIFICANCE FOR INITIATION OF DNA-REPLICATION

Inverted repeats occur nonrandomly in the DNA of most organisms. Stem- loops and cruciforms can form from inverted repeats. Such structures h ave been detected in pro- and eukaryotes. They may affect the supercoi ling degree of the DNA, the positioning of nucleosomes, the formation of other secondary structures of DNA, or directly interact with protei ns. Inverted repeats, stem-loops, and cruciforms are present at the re plication origins of phage, plasmids, mitochondria, eukaryotic viruses , and mammalian cells. Experiments with anti-cruciform antibodies sugg est that formation and stabilization of cruciforms at particular mamma lian origins may be associated with initiation of DNA replication. Man y proteins have been shown to interact with cruciforms, recognizing fe atures like DNA crossovers, four-way junctions, and curved/bent DNA of specific angles. A human cruciform binding protein (CBP)displays a no vel type of interaction with cruciforms and may be linked to initiatio n of DNA replication. (C) 1996 Wiley-Liss, Inc.