<p> Supplemental Material</p><p>Figs. S1-S5</p><p>Fig. S1. Diagram of pCT5gag-CFP. The plasmid expresses Gag-CFP in the context of a full-length genome with intact packaging signal and normal Rev and other viral protein synthesis except for Pol-encoded proteins and Env. A frame shift was also introduced into pCT5 to block cytopathicity in transfected human cells since this envelope glycoprotein can utilize human CXCR4 (Poeschla and Looney,1998).</p><p>1 Fig. S2. FIV Rev expression plasmid pCiRev is functional in an RRE reporter assay. 1.0 µg of CAT-RRE reporters for HIV-1 or FIV were transfected with 0.3 µg of the respective Rev-expressing plasmid or 0.3 µg empty vector plasmid with total DNA amount kept at 1.4 µg. 0.1 µg CMV-luc was co-transfected to control transfection efficiency.</p><p>2 Fig. S3. Time-lapse imaging of HeLa cells transfected with MS2-Cherry, FIVDY-24, FIVgag-CFP and FP93. One frame was acquired every 10s. Shown are frames 3 to 10. </p><p>3 Fig. S4. Plasma membrane accumulation of FIV genomic RNA depends on an intact packaging signal in 293T cells. Cells were transfected with (A) pFIVgag-CFP, pMS2-mCherry and pFIV-24 or (B) pFIVgag-CFP, pMS2-mCherry and pFIV-24, and live cell confocal imaging was performed 56 hours after transfectio</p><p>4 Fig. S5. MS2-GFP incorporation into HIV viral particles requires the MS2 stem- loops and an intact packaging sequence. 293T cells were transfected with 5ug pCMVR8.9 (lanes 1 to 4 and 6 to 9), 5ug pMS2-GFP (lanes 1 to 4 and 6 to 9), 5ug pHIV-24 (lanes 3 and 8), 5ug pHIV-24 (lanes 4 and 9) or 5ug pHIV-lacZ, lacking the twenty-four MS2 stem-loops (lanes 2 and 7). pcDNA3.1 (15ug) was transfected in lanes 5 and 10 as a control. Purified virions were lysed and separated on a 10% SDS-PAGE and probed with a mouse anti-GFP antibody (lanes 1 to 5) or a mouse anti HIV-1 p24 antibody (lanes 6 to 10).</p><p>5</p>