Model for the possible nuclear role of FV Gag during the late stages of infection. (1) Full length viral RNA export is still unknown. (2) After synthesis in the cytoplasm, Gag protein enters the nucleus via its NLS domain (located within the GRII box). In the nucleus, Gag could interact with the full length viral RNA via its GRI box favoring Gag-Gag interaction and subsequently unmasking Gag NES. (3) The nuclear export factor, CRM1, also called exportin 1, would then be able to interact with this ribonucleoprotein complex leading to its efficient nuclear export. (4) In the cytoplasm, Gag proteins will multimerize for capsid assembly near the MTOC. In the absence of Gag proteins, the initial nuclear export of unspliced PFV RNA could rely on another export mechanism independent of these proteins.