Schematic representation of templates, primers and products of RTion reactions. Only the 2 splice donor sites (SD1 and SD4) and the 2 splice acceptor sites (SA5 and SA7) important for this study are indicated. PCR-primer pairs used to specifically quantify the pNL4.3 plasmid (pNL), the FL cDNA or RNA (FL), and the Fspl cDNAs or RNAs (FSpl) are in gray, blue and red, respectively. Final proviral products corresponding to RTion of FL and FSpl RNAs are presented. RTion is a multi-step process and for clarity purposes, only the shortest intermediate RTion products detected with primer pairs specific for FL and FSpl are presented, as well as the shortest common ssDNA (yellow) and the U3 intermediate (green), respectively. All primer sequences and detailed PCR conditions will be provided on request.