Binding of Tat to TAR and recruitment of positive transcription elongation factor b occur independently in bovine immunodeficiency virus.
Transcriptional transactivators (Tat) from many lentiviruses interact with their cognate transactivation response RNA structures (TAR) to increase rates of elongation rather than initiation of transcription. For several of them, the complex of Tat and a species-specific cyclin T1 must be formed before the binding to TAR can occur with high affinity and specificity. In sharp contrast, Tat from the bovine immunodeficiency virus (BIV) binds to its TAR without the help of the cyclin T1. This binding depends on the upper stem and 5' bulge, but not the central loop in TAR. Moreover, cyclins T1 from different species can mediate effects of this Tat in cells. Unlike the situation with other lentiviruses, Tat transactivation can be rescued simply by linking a heterologous promoter to TAR in permissive cells. Thus, lentiviruses have evolved different strategies to recruit Tat and the positive transcription elongation factor b to their promoters, and interactions between Tat and TAR are independent from those between Tat and the cyclin T1 in BIV.
Barboric
M
M
Departments of Medicine and Microbiology and Immunology, University of California, San Francisco 94143-0703, USA.
Taube
R
R
Nekrep
N
N
Fujinaga
K
K
Peterlin
B M
BM
D000818:Animals; D019556:COS Cells; D002417:Cattle; D016895:Culture Media, Serum-Free; D056906:Cyclin T; D016213:Cyclins / Q000378:metabolism; D004285:Dogs; D015696:Gene Products, tat / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016087:Immunodeficiency Virus, Bovine / Q000235:genetics / Q000378:metabolism*; D042925:Positive Transcriptional Elongation Factor B; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism*; D013045:Species Specificity; D020079:Terminal Repeat Sequences; D015533:Transcriptional Activation
C503684:CCNT1 protein, human; D016895:Culture Media, Serum-Free; D056906:Cyclin T; D016213:Cyclins; D015696:Gene Products, tat; D012367:RNA, Viral; D042925:Positive Transcriptional Elongation Factor B; D017346:Protein Serine-Threonine Kinases