A DNA replication-arrest site RTS1 regulates imprinting by determining the direction of replication at mat1 in S. pombe

Abstract

Mating-type switching in Schizosaccharomyces pombe involves a strand-specific, alkali-labile imprint at the mat1 (mating-type) locus. The imprint is synthesized during replication in a swi1, swi3, and polymerase ␣ (swi7) dependent manner and is dependent on mat1 being replicated in a specific direction. Here we show that the direction of replication at mat1 is controlled by a cis-acting polar terminator of replication (RTS1). Two-dimensional gel analysis of replication intermediates reveals that RTS1 only terminates replication forks moving in the centromere-distal direction. A genetic analysis shows that RTS1 optimizes the imprinting process. Transposing the RTS1 element to the distal side of mat1 abolishes imprinting of the native mat1 allele but restores imprinting of an otherwise unimprinted inverted mat1 allele. These data provide conclusive evidence for the "direction of replication model" that explains the asymmetrical switching pattern of S. pombe, and identify a DNA replication-arrest element implicated in a developmental process. Such elements could play a more general role during development and differentiation in higher eukaryotes by regulating the direction of DNA replication at key loci.

The Escherichia coli Tus–Ter replication fork barrier causes site-specific DNA replication perturbation in yeast

“…Tof1 S.c. /Swi1 S.p. is required to establish RF pausing at diverse types of endogenous RF pause sites in yeast [3][4][5][6]11 . Interestingly, however, we observed that RF pausing at Tus-Ter modules was detectable in tof1 mutants ( Supplementary Fig.…”

“…Two of the best examples of these in yeast are the Fob1-mediated RF pause in the rDNA array in S. cerevisiae 2 , and the RTS1 barrier at the mating type locus in S. pombe 3 . One shared feature of these programmed RF pauses is that they rely on the evolutionarily conserved intra-S-phase checkpoint mediator, Tof1 S.c. /Swi1 S.p.…”

“…One shared feature of these programmed RF pauses is that they rely on the evolutionarily conserved intra-S-phase checkpoint mediator, Tof1 S.c. /Swi1 S.p. , to signal the presence of the RF barrier to the replisome and/or stabilize paused RFs [3][4][5][6] . Although these can be regarded as specialist RFpausing systems, both of these have been transferred successfully to ectopic genomic loci (within the same organism) to analyse the consequences of unscheduled RF pausing 5,7,8 .…”

Sap1p Binds to Ter1 at the Ribosomal DNA of Schizosaccharomyces pombe and Causes Polar Replication Fork Arrest

“…In addition, forks inevitably encounter natural replication fork barriers or termination (Ter) 2 sites in both prokaryotes and eukaryotes (3,4). Such Ter sites are usually polar or orientation-specific and, depending on the organism, presumably control proper completion of replication, chromosome segregation, recombination events, and even mating type switching in Schizosaccharomyces pombe (3)(4)(5). In Saccharomyces cerevisiae, polar fork arrest at the rDNA Ter sites presumably coordinates rDNA replication with transcription, regulates rDNA recombination, and controls the formation of extrachromosomal rDNA circles, which have been implicated in aging (6 -10).…”

A Complex Mechanism Determines Polarity of DNA Replication Fork Arrest by the Replication Terminator Complex of Bacillus subtilis

“…They have roles in a variety of tasks, including the coordination of DNA replication and transcription at eukaryotic rDNA loci (1,2), regulation of mating-type switching in yeast by strand-specific imprinting during replication (3,4), and participation in the final stages of bacterial chromosome replication and partitioning (5).…”