Acquisition of new proviral copies in avian lymphoid cells transformed by reticuloendotheliosis virus.
The expression of the v-rel oncogene of avian reticuloendotheliosis virus (REV-T) transforms and immortalizes very immature avian lymphoid cells. In REV-T-transformed lymphoid cells which were persistently infected with reticuloendotheliosis-associated virus (REV-A), the REV-T proviral copy number increases after the initial integration event. In 23 independently derived REV-T-transformed cell lines, 15 of the 18 virus-producing cell lines had acquired additional proviruses. The rate at which the newly acquired proviral sequences accumulated differed for various cell lines. In some cell lines, additional REV-T proviral copies could be detected as early as 8 months after the initial integration event. A correlation exists between the number of REV-T proviral sequences and the length of time which a given cell line had been propagated in culture. The integration sites occupied by the newly acquired REV-T proviruses were distinct. In contrast, reticuloendotheliosis-associated virus proviral sequences in these REV-T-transformed virus-producing lymphoid cells did not increase during in vitro culture. Furthermore, the acquisition of additional REV-T proviral sequences did not occur in non-virus-producing cell lines. Two of the newly acquired proviral sequences were molecularly cloned and analyzed by restriction endonuclease mapping. Although the newly acquired REV-T proviruses have not sustained major deletions, the viral sequences and the v-rel oncogene display numerous restriction enzyme polymorphisms. The cellular flanking sequences of two newly acquired REV-T proviruses analyzed were unique and shared no homology with flanking sequences of the other REV-T proviruses in these transformed cells. The nucleotide sequence of the virus-cellular DNA junctions of one newly acquired provirus and its cellular sequence prior to proviral integration were defined. A 5-base-pair direct repeat of cellular origin was present on each side of the long terminal repeat, indicating that the mechanism of acquisition of additional REV-T proviral sequences used reverse transcription and integration of new REV-T proviral copies.
Zhang
J Y
JY
Department of Microbiology, University of Texas, Austin 78712-1095.
Bose
H R
HR
D000818:Animals; D001483:Base Sequence; D002472:Cell Transformation, Viral; D002645:Chickens; D003001:Cloning, Molecular; D004279:DNA, Viral / Q000235:genetics*; D005784:Gene Amplification; D008214:Lymphocytes / Q000382:microbiology; D012194:RNA-Directed DNA Polymerase / Q000235:genetics; D011995:Recombination, Genetic; D015183:Restriction Mapping; D001356:Reticuloendotheliosis virus / Q000235:genetics*; D012190:Retroviridae / Q000235:genetics*; D013997:Time Factors
D004279:DNA, Viral; D012194:RNA-Directed DNA Polymerase