Saccharomyces cerevisiae encodes a single linker histone, Hho1p, with two 
globular domains. This raised the possibility that Hho1p could bind to two 
nucleosome cores simultaneously. To evaluate this idea, we studied the ability 
of a four-way junction, immobilized on the surface of a magnetic bead, to pull 
down a radiolabeled four-way junction in the presence of different Hho1 
proteins. Four-way junctions are known to bind to H1, presumably due to 
structure similarities to the DNA at the nucleosomal entry/exit point. We found 
a significant increase in the ability of full-length Hho1p to pull down 
radiolabeled four-way junction DNA under ionic conditions where both globular 
domains could bind. The binding was structure specific, since the use of 
double-stranded DNA, or a mutant Hho1p in which the second DNA binding site of 
globular domain 1 was abolished, resulted in a significant decrease in bridged 
binding. Additionally, bridged binding required a covalent attachment between 
the two globular domains, since factor Xa protease treatment of the complex 
formed by a modified Hho1p that contained a factor Xa cleavage site between the 
two globular domains resulted in a significant release of radiolabeled four-way 
junction. These findings demonstrated that the two globular domains 
independently associated with two different four-way junction molecules in a 
manner that required amino acid residues implicated in structure-specific 
binding in the nucleosome. We discuss the implication of these findings on the 
chromatin structure of yeast and propose a model where a single Hho1 protein 
binds to two serially adjacent nucleosomes.