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2018 ; 293
(28
): 11242-11250
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The epigenetic regulator SIRT7 guards against mammalian cellular senescence
induced by ribosomal DNA instability
#MMPMID29728458
Paredes S
; Angulo-Ibanez M
; Tasselli L
; Carlson SM
; Zheng W
; Li TM
; Chua KF
J Biol Chem
2018[Jul]; 293
(28
): 11242-11250
PMID29728458
show ga
In the yeast Saccharomyces cerevisiae, genomic instability in rDNA repeat
sequences is an underlying cause of cell aging and is suppressed by the
chromatin-silencing factor Sir2. In humans, rDNA instability is observed in
cancers and premature aging syndromes, but its underlying mechanisms and
functional consequences remain unclear. Here, we uncovered a pivotal role of
sirtuin 7 (SIRT7), a mammalian Sir2 homolog, in guarding against rDNA instability
and show that this function of SIRT7 protects against senescence in primary human
cells. We found that, mechanistically, SIRT7 is required for association of SNF2H
(also called SMARCA5, SWI/SNF-related matrix-associated actin-dependent regulator
of chromatin, subfamily A, member 5), a component of the nucleolar
heterochromatin-silencing complex NoRC, with rDNA sequences. Defective
rDNA-heterochromatin silencing in SIRT7-deficient cells unleashed rDNA
instability, with excision and loss of rDNA gene copies, which in turn induced
acute senescence. Mounting evidence indicates that accumulation of senescent
cells significantly contributes to tissue dysfunction in aging-related
pathologies. Our findings identify rDNA instability as a driver of mammalian
cellular senescence and implicate SIRT7-dependent heterochromatin silencing in
protecting against this process.