Antiviral Protein Ski8 Is a Direct Partner of Spo11 in Meiotic DNA Break Formation, Independent of Its Cytoplasmic Role in RNA Metabolism

Abstract

Meiotic recombination initiates with double-strand breaks (DSBs) catalyzed by Spo11 in conjunction with accessory proteins whose roles are not understood. Two-hybrid analysis reveals a network of interactions connecting the yeast DSB proteins to one another. Of these proteins, Ski8 was known to function in cytoplasmic RNA metabolism, suggesting that its role in recombination might be indirect. However, obligate partners of Ski8 in RNA metabolism are dispensable for recombination and Ski8 relocalizes to the nucleus and associates with chromosomes specifically during meiosis. Interaction of Ski8 with Spo11 is essential for DSB formation and Ski8 relocalization. Thus, Ski8 plays distinct roles in RNA metabolism and, as a direct partner of Spo11, in DSB formation. Ski8 works with Spo11 to recruit other DSB proteins to meiotic chromosomes, implicating Ski8 as a scaffold protein mediating assembly of a multiprotein complex essential for DSB formation.

Interactions between Mei4, Rec114, and other proteins required for meiotic DNA double-strand break formation in Saccharomyces cerevisiae

“…The findings in this study reinforce the view that has emerged from several lines of inquiry that there are at least four functionally distinct subgroups among the DSB proteins: Spo11-Ski8; Rec102-Rec104; Mer2-Mei4-Rec114; and Mre11-Rad50-Xrs2 (see Introduction) (Ohta et al 1998;Jiao et al 2003;Arora et al 2004;Kee et al 2004;Prieler et al 2005;Henderson et al 2006;Li et al 2006;Sasanuma et al 2007). To date, there is little support for the possibility that all of the DSB proteins together form a discrete "DSB holoenzyme," although available data cannot rule out this possibility.…”

“…Whereas several studies document physical and functional interactions connecting Ski8, Rec102, and Rec104 to Spo11, thus far relatively few direct connections are known to link Mer2, Mei4, and Rec114 to these other factors (Salem et al 1999;Kee and Keeney 2002;Jiao et al 2003;Arora et al 2004;Kee et al 2004;Henderson et al 2006;Li et al 2006). Recent findings concerning the structure of the REC102 gene help to address this lack.…”

“…Among the meiotically induced DSB proteins, Rec102 and Rec104 share perhaps the most intimate relationship with one another: they interact physically and genetically, they are mutually interdependent for proper chromosome localization, their behaviors are affected (or not) in parallel ways by mutations in other genes, and absence of either one exerts the same kind of effect (or not) on the behavior of other proteins (Salem et al 1999;Jiao et al 2003;Arora et al 2004;Kee et al 2004;Prieler et al 2005;Henderson et al 2006;Li et al 2006;Sasanuma et al 2007). The yeast two-hybrid results presented here further support this conclusion.…”

“…In vegetative cells it is part of a multiprotein complex in the cytoplasm that is involved in degradation and translational repression of nonpolyadenylated RNA (Masison et al 1995;Jacobs Anderson and Parker 1998;van Hoof et al 2000;Araki et al 2001). During meiosis, however, Ski8 relocalizes to the nucleus and associates with meiotic chromosomes where it acts as a direct partner of Spo11 Arora et al 2004). …”

“…Ski8 is a WD-repeat protein suggested to promote Spo11 interactions with other DSB proteins Arora et al 2004). The nuclease activity of Mre11 is required to remove Spo11 that has become covalently bound to DNA ends during DSB formation (Neale et al 2005), but this activity is dispensable for DSB formation per se (Alani et al 1990;Nairz and Klein 1997;Prinz et al 1997;Moreau et al 1999).…”