Termination of Chromosome Replication

This chapter discusses the components of the terminus-region replication fork-arrest system, their organization and structural features, and their functioning during termination of a round of vegetative replication in Bacillus subtilis. Progress in characterizing and understanding the components and features associated with termination of replication in B. subtilis and Escherichia coli proceeded almost in parallel. The current status of the dif system in B. subtilis is discussed in this chapter. There is emerging evidence to suggest that the replication fork trap might enable more efficient operation of this system. The basis for this will become apparent in the discussion of the various components and features associated with their operation. The functional fork-arrest complex contains two dimers of replication terminator protein (RTP) bound to overlapping A and B sites within the 30-bp terminator. Successful partitioning of replicated daughter chromosomes, generated upon completion of the termination phase of replication, requires the formation of completely separable chromosomes. The existence of multiple sequences of ~8 nt in length with a skewed distribution between the two strands of each oriC-terminus arm (replichore) of the chromosome has more recently been uncovered, and it is now clear that the polarity switch point for these sequences within the terminus region of E. coli coincides with dif. Finally, the chapter focuses on replication fork arrest near oriC under stringent conditions.