Transduction of the cellular src gene and 3' adjacent sequences in avian sarcoma virus PR2257

Barnier

et al. 1991

Self Cite

We previously described the isolation of the IC10 retrovirus which transduced the v-Rmil oncogene, a new member of the millraf gene family. This virus was generated during serial passaging of Rous-associated virus type 1 (RAV-1) in chicken embryo neuroretina (NR) cells and was selected for its ability to induce proliferation of these nondividing cells. IC10 was isolated after six passages of culture supernatants but was not detected in proliferating NR cells during early virus passages. In this study, we molecularly cloned and sequenced another v-Rmil-containing provirus, designated ICll, from NR cells infected at the third virus passage of the same experiment. Both IC1l and IC10 transduced only the serine/threonine kinase domain of c-Rmil. Comparison of v-Rmil and c-Rmil sequences indicated that amino-terminal truncation is sufficient to activate the mitogenic properties of c-Rmil. ICll and IC10 have identical 3' ends but differ by their 5' RAV-1-Rmil junctions. The 3' ends of both viruses were generated by recombination between Rmil and env genes, involving partial sequence identity. The 5' RAV-l-Rmil junction of ICll was formed by a splicing process between the RAV-1 leader and a 37-bp c-Rmil exon located upstream of the kinase domain. NR cells infected with this virus synthesize a unique Rmil protein. IC10 contains most of the gag gene recombined with v-Rmil and encodes a gag-Rmil hybrid protein. Serial passaging of ICll in NR cells led to the formation of a gag-Rmil-containing retrovirus. These results indicate that ICll represents an early step in transduction and that this virus further recombined with RAV-1 to generate IC10. They confirm our previously proposed model for the multistep generation of v-mil-transducing retroviruses. Therefore, activation and transduction of c-mil and c-Rmil, in NR cells infected with RAV-1, result from a common mechanism.

Section: Discussionsupporting

confidence: 62%

Common mechanism of retrovirus activation and transduction of c-mil and c-Rmil in chicken neuroretina cells infected with Rous-associated virus type 1

Felder

Barnier

et al. 1991

Self Cite

“…Similar structures were recently described in the 5' ends of two viruses which transduced the c-src gene (13,22). It is possible that the transduction of c-mil proceeded by the integration of RAV-1 provirus upstream of exon 8 of c-mil and the cotranscription of viral and c-mil sequences.…”

Section: Genomessupporting

confidence: 62%

“…Mechanism of c-mil transduction. There have been several reports on in vivo transduction of proto-oncogenes, including src (13,18,22), fps (35), erbB (21,32), and fos (36), by ALV. A general model for a multistep transduction of proto-oncogenes by ALV has been proposed (49).…”

Section: Genomesmentioning

confidence: 99%

Molecular and biological properties of c-mil transducing retroviruses generated during passage of Rous-associated virus type 1 in chicken neuroretina cells

Béchade

Marx

et al. 1990

Self Cite

IC1, IC2, and IC3 are novel c-mil transducing retroviruses generated during serial passaging of Rous-associated virus type 1 (RAV-1) in chicken embryo neuroretina cells. They were isolated by their ability to induce proliferation of these nondividing cells. IC2 and IC3 were generated during early passages of RAV-1 in neuroretina cells, whereas IC1 was isolated after six consecutive passages of virus supernatants. We sequenced the transduced genes and the mil-RAV-1 junctions of the three viruses. The 5' RAV-1-mil junction of IC2 and IC3 was formed by a splicing process between the RAV-1 leader sequence and exon 8 of the c-mil gene. The 5' end of IC1 resulted from homologous recombination between gag and mil sequences. Reconstitution experiments showed that serial passaging of IC2 in neuroretina cells also led to the formation of a gag-mil-containing retrovirus. Therefore, constitution of a U5-leader-delta c-mil-delta RAV-1-U3 virus represents early steps in c-mil transduction by RAV-1. This virus further recombined with RAV-1 to generate a gag-mil-containing virus. The three IC viruses transduced the serine/threonine kinase domain of the cellular gene. Hence, amino-terminal truncation is sufficient to activate the mitogenic property of c-mil. Comparison of the transforming properties of IC2 and IC1 showed that the transduced mil gene, expressed as a unique protein independent of gag sequences, was weakly transforming in avian cells. Acquisition of gag sequences by IC1 not only increased the rate of virus replication but also enhanced the transforming capacity of the virus.

“…Although hybrid virus-Aonc-poly(A) RNAs were previously described in avian lymphomatosis virus-infected cells (8,17), they were never shown to give rise to retroviruses. Conversely, similar 5' junctions were found in two avian sarcoma viruses which transduced the c-src gene in vivo (7,11). Therefore, splicing between viral leader and cellular sequences may represent a common mechanism for generating 5' junctions during the transduction process.…”

Section: Fig 1 (A)mentioning

confidence: 74%

Occurrence of alternatively spliced leader-delta onc-poly(A) transcripts in chicken neuroretina cells infected with Rous-associated virus type 1: implication in transduction of the c-mil/c-raf and c-Rmil/B-raf oncogenes

Felder

Laugier

et al. 1993

Self Cite

We previously reported that serial passaging of Rous-associated virus type 1 in nondividing chicken embryo neuroretina cells leads to reproducible generation of acutely mitogenic retroviruses that transduced the catalytic domain of c-millc-raf or c-RmilIB-raf. On the basis of structural analysis of several retroviruses, we proposed that the early step of oncogene transduction is the constitution of alternatively spliced leader-Aoncpoly(A) transcripts. Here, we show that neuroretina cells do synthesize hybrid leader-Amil and leader-ARmil RNAs and that these RNAs exhibit mitogenic properties and serve as templates for the generation of transducing retroviruses.