Functional cooperation between topoisomerase I and single strand DNA-binding protein

Protein-protein interactions play important role in cell biochemistry by fa vorably or adversely influencing major molecular events. In most documented cases, the interaction is direct between the partner molecules. Influence of activity in the absence of direct physical interaction between DNA trans action proteins is another important means of modulation. We show here that single strand binding protein stimulates DNA topoisomerase I activity with out direct protein-protein interactions. The stimulation is specific to top oisomerase I, as DNA gyrase activity is unaffected by SSB. We propose that such cases of functional collaboration between DNA transaction proteins pla y important roles in vivo. (C) 2001 Academic Press.