Data from: Heterochromatin suppresses gross chromosomal rearrangements at centromeres by repressing Tfs1/TFIIS-dependent transcription

Heterochromatin that is characterized by histone H3 lysine 9 (H3K9)
methylation assembles on repetitive regions including centromeres.
Although centromeric heterochromatin is important for faithful segregation
of chromosomes, its role in maintaining centromere integrity remains
elusive. Here, we found in fission yeast that heterochromatin suppresses
gross chromosomal rearrangements (GCRs) at centromeres. Mutations in
Clr4/Suv39 methyltransferase increased the formation of isochromosomes
whose breakpoints are present in centromere repeats. H3K9A and H3K9R
mutations also increased GCRs, suggesting that Clr4 appears to suppress
GCRs via H3K9 methylation. Both HP1 homologs, Swi6 and Chp2, and an RNAi
component Chp1 were the chromodomain proteins that are essential for full
suppression of GCRs. Remarkably, mutations in RNA polymerase II (RNAPII)
or the transcription factors including Tfs1/TFIIS which facilitates
restart of backtracked RNAPII specifically bypassed the requirement of
Clr4 to suppress GCRs. These results demonstrate that heterochromatin
suppresses GCRs by repressing Tfs1-dependent transcription of centromere
repeats.