BINDING TO 4-WAY JUNCTION DNA - A COMMON PROPERTY OF ARCHITECTURAL PROTEINS

Proteins that can be shown to strongly bind in vitro to the four-way ( Holliday) junction DNA include not only the obvious candidates such as enzymes involved in recombination, but also a remarkably diverse grou p of seemingly unrelated proteins, These include the HMG1 box proteins , members of the HMGI-Y family, winged helix proteins (including linke r histones), the SWI/SNF complex, and some totally unrelated prokaryot ic proteins, What these proteins seem to share is a propensity to bind to bent DNA, to bend DNA upon binding, and/or to preferentially inter act with DNA crossings, Thus, they appear to be, in the main, architec tural proteins, although some (like the SWI/SNF complex) have very spe cific functional roles as well, Perhaps because they bind to or promot e the formation of particular DNA structures, the four-way junction bi nding proteins are frequently interchangeable in cellular function, Fu rthermore, since a given kind of structure can be recognized by many d ifferent protein motifs, it is not surprising that apparently unrelate d proteins can fall into such a single functional class.