Fig. 3

PFV env is expressed by two major transcripts spliced to 3′ss–modification of the C element results in exclusive splicing to SA3. a Scheme of the locations of splice sites, of the C element and position of RT-PCR primers. b Detection of env 3′ splice sites by RT-PCR using a primer +1s and 5732a located downstream of the env start codon. Amplicons were separated on agarose gels and splice sites determined by nucleotide sequencing. c The mutation of the C element decreases genomic and pol transcripts. Foamy virus env is expressed by three transcripts alternatively spliced to SA2, SA3, and weakly to SA4. The Cn mutations results in splicing to SA3 and a reduction of genomic and pol mRNAs. The inactivation of SA3 (iSA3) partially recovers gag and pol expression