Table 2 Decapping and 59 / 39 exonuclease factors Factor Dcp1/Dcp2 Dcs1 (DcpS)/Dcs2 Lsm1–7 complex Xrn1 Rat1 Rai1 Pat1 Dhh1 Edc3 Scd6 Edc1/Edc2 Stm1 Sbp1 Tif51A Mrt4, Grc5, Sla2, Ths1 678 R. Parker Function mRNA decapping enzyme Dcp2: catalytic subunit: Nudix family member Releases m7GDP and 59p-RNA Dcp1: stimulatory subunit, Evh1/WH1 family member Blocked by eIF4E bound to cap Major cytoplasmic 59 to 39 exonuclease Processive and requires 59 monophosphate Stimulated by Dcs1/Dcs2 mRNA decapping enzymes with preference for short RNAs Releases m7Gp and ppN2 Cleaves m7GDP produced by Dcp1/Dcp2 to m7GMP and P Can affect stress responses Major nuclear 59 to 39 nuclease Paralog of Xrn1 Functions in nuclear RNA processing and decay Interacts with and stimulates Rat1 Contains mRNA cleavage site Releases m7GpppN2 and N2 May function in cap quality control Activates general mRNA decapping Serves as scaffolding protein for decapping complexes Both represses translation initiation and stimulates Dcp2 Interacts with Lsm1–7 complex and prefers to bind 39 end of oligoadenylated mRNA Promotes P-body assembly After deadenylation stabilizes 39 ends to 39 trimming Target of PKA kinase Required for efﬁcient decapping Forms heptometric ring complex and binds oligo- or deadenylated mRNAs May promote Pat1 conformational change to activate Dcp2 After deadenylation stabilizes 39 ends to 39 trimming Required for efﬁcient decapping of translating mRNAs Member of ATP-dependent DExD/H box RNA helicase family Inhibits translation initiation in vitro upstream of 48S complex formation Accumulates in both stress granules and P-bodies Interacts with Dcp2, Pat1, Scd6, Edc3 RNA-binding protein Binds and directly stimulates Dcp2 Plays major role in aggregation of P-bodies and serves as scaffold for decapping factors Not generally required for mRNA decapping unless Dcp1/Dcp2 is limited RNA-binding protein related to Edc3 Genetic interaction with Edc3 and synthetic decapping defect in edc3Δ scd6Δ Represses translation by binding eIF4G Interacts with Dhh1, Dcp2, Pat1 May be mRNA-speciﬁc decapping/translation regulatory factor Two small RNA-binding proteins Directly bind and stimulate Dcp1/Dcp2 Ribosome-binding protein Can stimulate Dhh1-dependent decapping Typically required only for subset of mRNAs decapping Stalls 80S complex after translation initiation Abundant RNA-binding protein Overexpression suppresses pat1Δ defects by enhancing Dhh1 function Binds eIF4G to repress translation initiation Translation initiation factor eIF5A Speciﬁc mutations inhibit decapping Mechanism is not known Additional proteins affecting mRNA turnover by unknown mechanism References Schwartz and Parker (2000); She et al. (2004, 2008); Deshmukh et al. (2008) Kenna et al. (1993); Poole and Stevens (1995); Van Dijk et al. (2003); Malys et al. (2004); Liu and Kiledjian (2005); Jinek et al. (2011) Johnson (1997); Xiang et al. (2009) Xue et al. (2000); Xiang et al. (2009); Jiao et al. (2010) Bouveret et al. (2000); Tharun et al. (2000); Chowdhury et al. (2007); Pilkington and Parker (2008); Nissan et al. (2010); Ramachandran et al. (2011) Boeck et al. (1998); Bouveret et al. (2000); Tharun et al. (2000); Chowdhury et al. (2007) Coller et al. (2001); Fischer and Weiss (2002); Coller and Parker (2005); Swisher and Parker (2009); Nissan et al. (2010) Badis et al. (2004); Kshirsagar and Parker (2004); Decker et al. (2007); Dong et al. (2007); Harigaya et al. (2010) Decourty et al. (2008); Nissan et al. (2010); Rajyaguru et al. (2011) Dunckley et al. 2001; Schwartz et al. (2003); Neef and Thiele (2009); Borja et al. (2011) Balagopal and Parker (2009, 2011) Segal et al. (2006); Rajyaguru et al. (2011) Zuk and Jacobson (1998) Zuk et al. (1999)