An RNA secondary structure juxtaposes two remote genetic signals for human T-cell leukemia virus type I RNA 3'-end processing.
Sequence analysis of the human T-cell leukemia virus type I (HTLV-I) long terminal repeat (LTR) does not reveal a polyadenylation consensus sequence, AAUAAA, close to the polyadenylation site at the 3' end of the viral RNA. Using site-directed mutagenesis, we demonstrated that two cis-acting signals are required for efficient RNA processing in HTLV-I LTR: (i) a remote AAUAAA hexamer at a distance of 276 nucleotides upstream of the polyadenylation site, and (ii) the 20-nucleotide GU-rich sequence immediately downstream from the poly(A) site. It has been postulated that the folding of RNA into a secondary structure juxtaposes the AAUAAA sequence, in a noncontiguous manner, to within 14 nucleotides of the polyadenylation site. To test this hypothesis, we introduced deletions and point mutations within the U3 and R regions of the LTR. RNA 3'-end processing occurred efficiently at the authentic HTLV-I poly(A) site after deletion of the sequences predicted to form the secondary structure. Thus, the genetic analysis supports the hypothesis that folding of the HTLV-I RNA in the U3 and R regions juxtaposes the AAUAAA sequence and the poly(A) site to the correct functional distance. This unique arrangement of RNA-processing signals is also found in the related retroviruses HTLV-II and bovine leukemia virus.
Bar-Shira
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Department of Molecular Genetics, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Panet
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Honigman
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D001483:Base Sequence; D002460:Cell Line; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D002872:Chromosome Deletion; D003001:Cloning, Molecular / Q000379:methods; D015342:DNA Probes; D005814:Genes, Viral; D005822:Genetic Vectors; D015368:Human T-lymphotropic virus 1 / Q000235:genetics*; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009690:Nucleic Acid Conformation; D015345:Oligonucleotide Probes; D011061:Poly A / Q000235:genetics / Q000302:isolation & purification; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger; D012367:RNA, Viral / Q000737:chemistry / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid; D012190:Retroviridae / Q000235:genetics; D014162:Transfection
D015342:DNA Probes; D015345:Oligonucleotide Probes; D012333:RNA, Messenger; D012367:RNA, Viral; D011061:Poly A; D012313:RNA; D015500:Chloramphenicol O-Acetyltransferase