Survival of motor neurons (SMN) complex is composed by SMN and a class of proteins called Gemins, which localize in both cytoplasm and nucleoplasm [210, 211] . Gemin7 and Gemin8 constitute the core of the complex where the other Gemins associate by means of numerous proteinprotein interactions from the periphery. The SMN complex is involved in the biogenesis of uridine-rich small nuclear ribonucleoprotein (U snRNP) in the cytoplasm and then the U snRNP carries out the splicing of pre-mRNAs in the nucleus [212] [213] [214] . The snRNPs are composed of the major U snRNAs U1, U2, U4, U5, and U6 as well as a group of seven proteins known as Sm ribonucleoproteins that collectively make up the extremely stable Sm core of the snRNP. Gemins (except Gemin-2) associate with Sm proteins to form a heptameric ring structure in the presence of U snRNAs [211] . After Sm core assembly, the U snRNPs are imported to the nucleus, localizing in foci known as Cajal Bodies, where further maturation processes take place [215] . Gemin-3, one of the main components of SMN complex, is cleaved in PV-infected HeLa cells leading to a 50 KDa cleavage product. Scission of Gemin-3 negatively impacts on the kinetics of Sm core assembly, which is prevented in presence of inhibitors of PV replication [216] . These results indicated that high levels of PV proteins are required for this process to occur, as is the case of Nup153, Nup62, and eIF4GII, [16, 122] . PV 2A pro is able to hydrolyze purified Gemin-3 in vitro, rendering a cleavage product similar to that found in PV-infected HeLa cells [216] . Only one potential 2A procleavage site, between the amino acids Tyr 462 and Gly 463 (VHTYG), was found in this SMN complex component. Proteolysis of Gemin-3 at this position would render two cleavage products of about 50-30 KDa, in agreement with the polypeptide of about 50 KDa found in PV-infected and 2A pro -expressing cells. In addition, G463E mutation avoids direct hydrolysis of Gemin-3 exerted by PV 2A pro in vivo and in vitro [216] . Taken together, these findings support the notion that VHTYG is the cleavage site for PV 2A pro in Gemin-3. Although hydrolysis of Gemin-3 is exerted in cells transfected with plasmid encoding PV 2A pro , it does not take place when this protease is expressed from exogenous mRNAs; contrary to that found with eIF4GI, eIF4GII, Nup98, Nup153 and Nup62 [17] (and unpublished data). A probable explanation for this difference is that PV 2A pro is expressed at lower levels from transfected mRNAs than from plasmids [95] (Castello et al., 2006) . Thus, Gemin-3 cleavage may be a very late event in PV-infected cells because it requires expression of high amounts of PV 2A pro . Gemin-3 hydrolysis may directly impact on pre-mRNA splicing since this event reduces the availability of SMN complexes, which is involved in U snRNPs biogenesis. Nevertheless, Alstead and colleagues could not detect any apparent effect of Gemin-3 proteolysis in splicing of cellular pre-mRNAs [216] . Therefore, the physiological relevance of Gemin-3 cleavage in PV biological cycle remains unknown. In addition to eIFs, Nups and proteins from SMN complex, PV 2A pro is able to cleave proteins involved in other cellular processes, such as transcription. TBP is cleaved by PV 2A pro between amino acids Tyr 34 and Gly 35 in vitro, although this cleavage only removes the first 34 aa located at the N-terminus and does not inhibit transcription carried out by RNA Polymerase II [217, 218] . These findings are in agreement with the fact that host mRNA transcription takes place in 2A pro -expressing cells when both translation and RNA nuclear export are inhibited, upon cleavage of eIF4G and Nups [17] . One attractive hypothesis is that PV 2A pro could cleave specific initiation factors affecting specific rather than general mRNA transcription in order to modulate host-cell response to viral infection. Further studies in this direction can be carried out using microarray platforms to detect precise alterations in cellular transcriptome after PV-infection or 2A pro expression. These studies could be complemented by screening for new host factors cleaved by PV 2A pro using different in silico and experimental approaches.