Numerous mRNAs are degraded in processing bodies (P bodies) in Saccharomyces 
cerevisiae. In logarithmically growing cells, only 0-1 P bodies per cell are 
detectable. However, the number and appearance of P bodies change once the cell 
encounters stress. Here, we show that the polysome-associated mRNA-binding 
protein Scp160 interacts with P body components, such as the decapping protein 
Dcp2 and the scaffold protein Pat1, presumably, on polysomes. Loss of either 
Scp160 or its interaction partner Bfr1 caused the formation of Dcp2-positive 
structures. These Dcp2-positive foci contained mRNA, because their formation was 
inhibited by the presence of cycloheximide. In addition, Scp160 was required for 
proper P body formation because only a subset of bona fide P body components 
could assemble into the Dcp2-positive foci in Δscp160 cells. In either Δbfr1 or 
Δscp160 cells, P body formation was uncoupled from translational attenuation as 
the polysome profile remained unchanged. Collectively, our data suggest that 
Bfr1 and Scp160 prevent P body formation under normal growth conditions.