Figure 2

Retroviruses target the MTOC during the early and/or the late phase of the viral replication cycle. Retroviruses enter into the host cell mainly by receptor-mediated fusion of the viral envelope with the plasma membrane (1). After crossing the actin cortex, the viral core is released into the cytoplasm where it undergoes a process of uncoating during which the viral genomic RNA (black) is reverse transcribed into a double-strand linear DNA copy (red) (2). Incoming viral cores en route to the nucleus reach the MTOC by using the molecular motor complexes to traffic along the MTs (3). In the nucleus the viral DNA genome is stably integrated into the host cell chromosome (4). The integrated viral DNA or provirus is the template for the synthesis of the viral mRNAs (5) which are transported in the cytoplasm and translated to produce the viral Gag polyproteins and the viral envelope glycoproteins(6). Newly synthesized Gag proteins and the viral genomic RNA converge to the MTOC where encapsidation and assembly initiate (7a). At this late stage, FVs are characterized by a second reverse transcription event (7b). By trafficking along the MT network assembling viral particles reach the plasma or endosomal membranes where budding occurs (8a and b). Finally, for most retroviruses, a process known as maturation is necessary for the generation of infectious viruses able to begin a new round of infection (9).