title: The AFF4 scaffold binds human P-TEFb adjacent to HIV Tat.
abstract: Human positive transcription elongation factor b (P-TEFb) phosphorylates RNA polymerase II and regulatory proteins to trigger elongation of many gene transcripts. The HIV-1 Tat protein selectively recruits P-TEFb as part of a super elongation complex (SEC) organized on a flexible AFF1 or AFF4 scaffold. To understand this specificity and determine if scaffold binding alters P-TEFb conformation, we determined the structure of a tripartite complex containing the recognition regions of P-TEFb and AFF4. AFF4 meanders over the surface of the P-TEFb cyclin T1 (CycT1) subunit but makes no stable contacts with the CDK9 kinase subunit. Interface mutations reduced CycT1 binding and AFF4-dependent transcription. AFF4 is positioned to make unexpected direct contacts with HIV Tat, and Tat enhances P-TEFb affinity for AFF4. These studies define the mechanism of scaffold recognition by P-TEFb and reveal an unanticipated intersubunit pocket on the AFF4 SEC that potentially represents a target for therapeutic intervention against HIV/AIDS. DOI:http://dx.doi.org/10.7554/eLife.00327.001.
authors.affiliation: Department of Molecular and Cell Biology , University of California, Berkeley , Berkeley , United States.
authors.forename: Ursula
authors.initials: U
authors.lastname: Schulze-Gahmen
authors.forename: Heather
authors.initials: H
authors.lastname: Upton
authors.forename: Andrew
authors.initials: A
authors.lastname: Birnberg
authors.forename: Katherine
authors.initials: K
authors.lastname: Bao
authors.forename: Seemay
authors.initials: S
authors.lastname: Chou
authors.forename: Nevan J
authors.initials: NJ
authors.lastname: Krogan
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhou
authors.forename: Tom
authors.initials: T
authors.lastname: Alber
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D056906:Cyclin T / Q000378:metabolism; D042863:Cyclin-Dependent Kinase 9 / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D015497:HIV-1 / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D042925:Positive Transcriptional Elongation Factor B / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D011994:Recombinant Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D061805:Transcription Elongation, Genetic; D035602:Transcriptional Elongation Factors; D014779:Virus Replication; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000737:chemistry / Q000378:metabolism*
chemical_list: C471348:AFF4 protein, human; C503684:CCNT1 protein, human; D056906:Cyclin T; D011994:Recombinant Proteins; D012097:Repressor Proteins; D035602:Transcriptional Elongation Factors; D054322:tat Gene Products, Human Immunodeficiency Virus; D042925:Positive Transcriptional Elongation Factor B; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9
keywords: Human; SEC; intrinsically disordered proteins; super elongation complex; transcription elongation