Characterization of a Rous sarcoma virus mutant defective in packaging its own genomic RNA: biochemical properties of mutant TK15 and mutant-induced transformants

We demonstrated that molecular clones of the v-myb oncogene of avian myeloblastosis virus (AMV) can direct the synthesis of p48v-mYb both in avian and mammalian cells which are not targets for transformation by AMV. To accomplish this, we constructed dominantly selectable avian leukosis virus derivatives which efficiently coexpress the protein products of the TnS neo gene and the v-myb oncogene. The use of chemically transformed QT6 quail cells for proviral DNA transfection or retroviral infection, followed by G418 selection, allowed the generation of cell lines which continuously produce both undeleted infectious neo-myb viral stocks 267 iqw MUMA on July 6, 2020 by guest http://jvi.asm.org/ Downloaded from virus is a member of the src gene family. Cell 35:71-78.

Section: Discussionmentioning

confidence: 99%

Expression of molecular clones of v-myb in avian and mammalian cells independently of transformation

Lipsick¹,

Ibañez²,

Baluda³

1986

“…Since env mRNA uses the same leader sequence as gag-pol mRNA (7,9), it is unlikely that the expression of gag and pol are affected in the mutants described here. This suggestion is supported by the fact that two distinct natural avian retroviral packaging mutants, SE21Q1b (23) and TK15 (12,18), which have deletions of approximately 150 and 250 nucleotides in the leader region, respectively, apparently express normal levels of gag proteins.…”

mentioning

confidence: 97%

“…Two additional regions which are apparently required for packaging have been identified in the ASV genome. Through analysis of two independent natural viral mutants (12,18,23), it has been shown that a packaging-deficient phenotype is associated with large deletions (150 to 250 nucleotides) in the 5' noncoding leader region (positions 1 to 380) ( Fig. 1).…”

mentioning

confidence: 99%

A conserved cis-acting sequence in the 5' leader of avian sarcoma virus RNA is required for packaging

Katz¹,

Terry²,

Skalka³

1986

116

The deletion of a conserved sequence of ca. 30 nucleotides in the 5' noncoding leader region of an avian sarcoma virus DNA clone resulted in a loss of infectivity after transfection of chicken embryo fibroblasts. Genetic and biochemical analysis of a representative mutant demonstrated that the env gene was expressed normally. Thus, viral RNA transcription, splicing, and translation were not impaired. The amount of mutant viral RNA encapsidated into virions, however, was severely reduced despite the presence of helper-virus. We conclude that the deleted sequence is an essential cis-acting packaging signal.

“…The specificity with which retroviral full-length genomic RNAs are encapsidated suggests that specific sequences are required for RNA selection. These cis-acting sequences, called packaging (Psi), or encapsidation, signals, have been identified in avian, murine, and primate retroviruses (13,14,17,19,23). For Moloney murine leukemia virus (M-MuLV) and human immunodeficiency virus (HIV), packaging signals are located between splice sites and therefore are not contained in the subgenomic mRNAs.…”

mentioning

confidence: 99%

Nucleocapsid protein effects on the specificity of retrovirus RNA encapsidation

Zhang

Barklis

1995

134

We have analyzed the roles of Gag protein nucleocapsid (NC) domains in the packaging or encapsidation of retroviral RNAs into virus particles. We found that mutation of both zinc finger motifs of the human immunodeficiency virus (HIV) NC domain reduced but did not eliminate encapsidation of the HIV viral RNA. However, the NC mutations also resulted in a three-to fourfold reduction in the specificity of RNA encapsidation, as determined by comparison of virus-associated genomic and spliced RNA levels. As a complementary approach, we replaced the NC domain of Moloney murine leukemia virus (M-MuLV) with that of HIV.