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2016 ; 125
(3
): 523-33
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Linking replication stress with heterochromatin formation
#MMPMID26511280
Nikolov I
; Taddei A
Chromosoma
2016[Jun]; 125
(3
): 523-33
PMID26511280
show ga
The eukaryotic genome can be roughly divided into euchromatin and heterochromatin
domains that are structurally and functionally distinct. Heterochromatin is
characterized by its high compaction that impedes DNA transactions such as gene
transcription, replication, or recombination. Beyond its role in regulating DNA
accessibility, heterochromatin plays essential roles in nuclear architecture,
chromosome segregation, and genome stability. The formation of heterochromatin
involves special histone modifications and the recruitment and spreading of
silencing complexes that impact the higher-order structures of chromatin;
however, its molecular nature varies between different chromosomal regions and
between species. Although heterochromatin has been extensively characterized, its
formation and maintenance throughout the cell cycle are not yet fully understood.
The biggest challenge for the faithful transmission of chromatin domains is the
destabilization of chromatin structures followed by their reassembly on a novel
DNA template during genomic replication. This destabilizing event also provides a
window of opportunity for the de novo establishment of heterochromatin. In recent
years, it has become clear that different types of obstacles such as tight
protein-DNA complexes, highly transcribed genes, and secondary DNA structures
could impede the normal progression of the replisome and thus have the potential
to endanger the integrity of the genome. Multiple studies carried out in
different model organisms have demonstrated the capacity of such replisome
impediments to favor the formation of heterochromatin. Our review summarizes
these reports and discusses the potential role of replication stress in the
formation and maintenance of heterochromatin and the role that silencing proteins
could play at sites where the integrity of the genome is compromised.
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