"Chromosome kissing" and modulation of replication termination

Abstract

Previously, inter-chromosomal interactions called "chromosome kissing" have been reported to control tissue-specific transcription and cell fate determination. Using the fission yeast as a model system we have shown that physiologically programmed replication termination is also modulated by chromosome kissing. The published report reviewed here shows that a myb-like replication terminator protein Reb1 of S. pombe and its cognate binding sites (Ter) are involved in chromosome kissing that promotes a cooperative mechanism of replication termination. We also suggest that at least one other replication terminator protein namely Sap1, which is also an origin binding protein, is likely to be involved in a similar mechanism of control not only of fork arrest but also of replication initiation and in possible ori-Ter interaction. We discuss the roles of chromatin remodeling and other proteins in this novel mechanism of replication control.

Figure 1

Schematic diagram of the nontranscribed spacer region of rDNA of S. pombe. (A) The 3 Ter sites, the direction of replication and transcription and their points of arrest are shown; (B) diagrammatic representation of the Reb1 protein showing the N-terminal dimerization domain, the myb-associated domain (which has SANT motifs) and the two myb domains that are involved in DNA binding.

Figure 2

A diagrammatic representation of the 4C technique used to determine chromosome kissing at the Ter sites located in chromosome 1 and chromosome 2 of fission yeast.