The N-terminus of the NSP3 homodimer of rotavirus A (RV-A...

The N-terminus of the NSP3 homodimer of rotavirus A (RV-A) interacts with the 3' end of viral mRNAs, while the C-terminus binds to the eIF4G (EIF4G1), a component of the EIF4F complex, involved in translation initiation (Piron et al. 1999: bovine RV-A strain RF was used; Vende et al. 2000: bovine RV-A strain SF was used and EIF4G1 of unspecified origin; Groft and Burley 2002: simian RV-A strain SA11 was used and human EIF4G1; Gratia et al. 2015: RV-A SF strain was used and human EIF4G1). In this manner, NSP3 plays a role similar to the role of PABP (PABPC1), which simultaneously binds to the polyA tail of mRNAs and to the EIF4F complex (Vende et al. 2000, Groft and Burley 2002). As another component of the EIF4F complex, EIF4E, interacts with the capped 5' terminus of mRNAs, the interaction of EIF4G1 with the 3' end of mRNAs through PABP, for polyadenylated mRNAs, or through NSP3, for rotavirus RNAs, enables circularization of mRNAs (Groft and Burley 2002). The simultaneous interaction of NSP3 with RV-A mRNAs and the EIF4F complex is required for efficient mRNA translation (Vende et al. 2000, Gratia et al. 2015). NSP3-mediated stimulation of mRNA translation involves stabilization of interaction between EIF4G1 and EIF4E subunits of the EIF4F complex upon NSP3 binding (Gratia et al. 2015). NSP3 proteins from different RV-A strains show different levels of translation enhancement (Gratia et al. 2015).

ZC3H7B (also known as RoXaN, for Rotavirus X-associated non-structural protein) is a multi-domain RNA-binding cellular protein that interacts with the dimerization domain of rotavirus NSP3 to form a ternary complex with NSP3 and eIF4G1 that excludes PABPC1 (Vitour et al. 2004: bovine RV-A strain RF and human recombinant proteins were used; Harb et al. 2008: RF virus strain and human recombinant proteins were used).