U3 sequences from HTLV-I and -II LTRs confer pX protein response to a murine leukemia virus LTR.
Human T-cell leukemia virus (HTLV) types I and II are unusual among replication-competent retroviruses in that they contain a fourth gene (chi) necessary for replication. The chi gene product, p chi, transcriptionally transactivates the viral long repeat (LTR), and is thus a positive regulator. To investigate p chi transactivation, sequences from the U3 regions of the LTRs of HTLV-I and -II were inserted into the Moloney murine leukemia virus (M-MuLV) LTR by recombinant DNA techniques. Transient expression assays of the chimeric LTRs indicated that the HTLV sequences conferred to the M-MuLV LTR responsiveness to HTLV p chi protein. M-MuLV enhancers were not required for function of the chimeric LTRs. Infectious recombinant M-MuLVs containing chimeric LTRs were also generated. These viruses showed higher infectivity when assayed in mouse cells expressing HTLV-II p chi protein compared to normal mouse cells. Thus the HTLV sequences were able to confer p chi responsiveness to infectious M-MuLV. The generation of a virus dependent on a transactivating protein for its replication has implications for the evolution of the human T-cell leukemia viruses.
D004279:DNA, Viral / Q000235:genetics*; D017977:Deltaretrovirus / Q000235:genetics*; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation; D008979:Moloney murine leukemia virus / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012091:Repetitive Sequences, Nucleic Acid; D012191:Retroviridae Proteins / Q000235:genetics*; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics*; D014158:Transcription, Genetic; D014779:Virus Replication
D004279:DNA, Viral; D012191:Retroviridae Proteins; D015534:Trans-Activators; D014157:Transcription Factors