Tat-responsive region RNA of human immunodeficiency virus type 1 stimulates protein synthesis in vivo and in vitro: relationship between structure and function.
The Tat-responsive region (TAR) sequence is present at the 5' end of human immunodeficiency virus 1 mRNAs and as a cytoplasmic form of 58-66 nucleotides. TAR RNA blocks the activation and autophosphorylation of the double-stranded RNA-activated protein kinase in vitro. We show here that TAR RNA also prevents the double-stranded RNA-mediated inhibition of translation in a cell-free system. Mutagenic and structural analyses of TAR RNA indicate that a stem of at least 14 base pairs is required for this activity, whereas the loop and bulge required for transactivation by Tat are dispensable. Truncation of the RNA to 68 nucleotides results in the loss of translational rescue ability, suggesting that the short cytoplasmic TAR RNA produced by viral transcription in vivo may not have the capability to suppress activation of the kinase. However, because longer TAR transcripts stimulate expression in a transient assay in vivo, the TAR structure at the 5' end of viral mRNAs could still exert this function in cis.
Gunnery
S
S
Cold Spring Harbor Laboratory, NY 11724.
Green
S R
SR
Mathews
M B
MB
D001483:Base Sequence; D004252:DNA Mutational Analysis; D015967:Gene Expression Regulation, Viral; D015696:Gene Products, tat / Q000235:genetics*; D015497:HIV-1 / Q000235:genetics*; D006860:Hydrogen Bonding; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010766:Phosphorylation; D014176:Protein Biosynthesis; D011494:Protein Kinases / Q000378:metabolism*; D012330:RNA, Double-Stranded / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000648:ultrastructure; D012367:RNA, Viral / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid; D013329:Structure-Activity Relationship; D019892:eIF-2 Kinase; D054322:tat Gene Products, Human Immunodeficiency Virus
D015696:Gene Products, tat; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D012367:RNA, Viral; D054322:tat Gene Products, Human Immunodeficiency Virus; D011494:Protein Kinases; D019892:eIF-2 Kinase