DRUSE

Karim Mekhail and colleagues studied a network in the the budding yeast Saccharomyces cerevisiae that stabilizes ribosomal DNA repeats thru interactions between rDNA-associated silencing proteins and proteins of the inner nuclear membrane (INM).

They reported that deletion of either the INM or silencing proteins:

—reduces perinuclear rDNA positioning

—disrupts the nucleolus–nucleoplasm boundary

—induces the formation of recombination foci

—destabilizes the rDNA repeats

“In addition, artificial targeting of rDNA repeats to the INM suppresses the instability observed in cells lacking an rDNA-associated silencing protein that is typically required for peripheral tethering of the repeats.

Moreover, in contrast to Sir2 and its associated nucleolar factors, the INM proteins are not required for rDNA silencing, indicating that Sir2-dependent silencing is not sufficient to inhibit recombination within the rDNA locus.

These findings demonstrate a role for INM proteins in the perinuclear localization of chromosomes and show that tethering to the nuclear periphery is required for the stability of rDNA repeats.”

[for more details]

Their results suggest that Sir2-dependent silencing alone cannot inhibit recombination within the repetitive rDNA locus and that INM-mediated perinuclear chromosome tethering ensures repeat stability.

They expect that the proteins studied are members of perinuclear networks that control recombination at multiple loci to maintain genome stability.