FBI-1, a factor that binds to the HIV-1 inducer of short transcripts (IST), is a POZ domain protein.
The HIV-1 promoter directs the synthesis of two classes of transcripts, short, non-polyadenylated transcripts and full-length, polyadenylated transcripts. The synthesis of short transcripts is activated by a bipartite DNA element, the inducer of short transcripts or IST, located downstream of the HIV-1 transcriptional start site, while the synthesis of full-length transcripts is activated by the viral activator Tat. Tat binds to the RNA element TAR, which is encoded largely between the two IST half-elements. Upon activation by Tat, the synthesis of short RNAs is repressed. We have previously purified a factor called FBI-1 (for factor that binds to IST) whose binding to wild-type and mutated ISTs correlated well with the abilities of these ISTs to direct the synthesis of short transcripts. Here, we report the cloning of cDNAs encoding FBI-1. FBI-1 contains a POZ domain at its N-terminus and four Krüppel-type zinc fingers at its C-terminus. The C-terminus is sufficient for specific binding, and FBI-1 can form homomers through its POZ domain and, in vivo, through its zinc finger domain as well. In addition, FBI-1 associates with Tat, suggesting that repression of the short transcripts by Tat may be mediated through interactions between the two factors.
Morrison
D J
DJ
Undergraduate Program, Department of Pharmacology, State University of New York at Stony Brook, Stony Brook, NY 11794, USA.
Pendergrast
P S
PS
Stavropoulos
P
P
Colmenares
S U
SU
Kobayashi
R
R
Hernandez
N
N
D000595:Amino Acid Sequence; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015696:Gene Products, tat / Q000378:metabolism; D015497:HIV-1 / Q000235:genetics*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012996:Solutions; D016335:Zinc Fingers; D054322:tat Gene Products, Human Immunodeficiency Virus