Figure 9. Model of the nuclear exosome complex.

The schematic representation shows the architecture of the yeast nuclear exosome based on current structural and biochemical information. The exosome core (Exo-10) is depicted with the RNase PH-like subunits in gray, the S1/KH subunits in orange and Rrp44 in pink (based on the structure reported in Makino et al, 2013a). RNA is shown in black, threading through the internal channel and reaching the exoribonuclease site of Rrp44 (highlighted with a circle). The endonuclease site in the PIN domain of Rrp44 is also highlighted with a circle. Rrp6 is shown in red, with the exoribonuclease site highlighted as a circle. The exoribonuclease of Rrp6, depicted based on Midtgaard et al, 2006; is positioned near the exosome-binding domain of Rrp6, as determined by Makino et al, 2013a;. Rrp47 is in gray while Mtr4 is in blue. The channel in the helicase core and the insertion domain of Mtr4 are indicated in the model (according to the structures reported by Jackson et al, 2010; Weir et al, 2010). The N-terminus of Mtr4 binds at the interface between Rrp6 and Rrp47. The N-terminal interaction regions of Rrp6, Rrp47 and Mtr4 are denoted by N. Mpp6 is shown tentatively at the top of Exo-10, as its binding is not dependent on Rrp44.