Transduction of the human insulin gene via retroviral vectors fails to yield spliced transcripts

The rat interleukin-5 gene: characterization and expression by retroviral gene transfer and polymerase chain reaction

The rat interleukin-5 (IL-5) gene was isolated from a genomic lambda phage library and a fragment containing all four exons was inserted into the retroviral vector pXT1, resulting in pXTRIL5. Upon retroviral gene transfer into two IL-5-dependent mouse cell lines, B13 and T88M, autonomously growing cells were established and B-cell growth factor activity was detected in the supernatants of the infected cells. "cDNA" versions of the rat IL-5 gene were rescued by the polymerase chain reaction (PCR) with primers specific for the flanking regions of the cloning site in pXT1. Restriction or DNA sequence analysis of five different clones revealed precise splicing in two cases, while three of the clones had retained the first intron. In addition, in two of these about 400 bp of rat IL-5 5' flanking regions were deleted. The sequence comparison of rat, mouse, and human IL-5 genes revealed a high degree of conservation (e.g., mouse and rat were 92% homologous at the amino acid level). The combination of retroviral gene transfer and PCR may offer an alternative, efficient method for the cloning of cDNAs.

Deletion in a recombinant retroviral vector resulting from a cryptic splice donor signal in the Moloney leukemia virus envelope gene

Proviral DNA derived from a recombinant retroviral vector (LHMlPL), constructed to transduce the human purine nucleoside phosphorylase coding region along with the mouse metallothionein l promoter, was molecularly cloned in order to characterize a deletion previously observed in this provirus. Nucleotide sequence comparison with the original retroviral vector construct revealed two deletions in the cloned provirus. One of the deleted regions originated entirely from within the mouse metallothionein promoter. A second deletion eliminated portions of both viral and metallothionein promoter sequences. All four deletion junctions in the original construct included sequences which conform to those proposed as eukaryotic consensus splice donor and acceptor signals, including a previously unreported cryptic splice donor signal in the Moloney leukemia virus envelope gene. It is concluded that RNA splicing between inadvertently juxtaposed donor and acceptor signals was responsible for the observed deletions.