Recruitment of human cyclin T1 to nuclear bodies through direct interaction with the PML protein.
Human cyclin T1, the cyclin partner of Cdk9 kinase in the positive transcription elongation factor b (P-TEFb), is an essential cellular cofactor that is recruited by the human immunodeficiency virus type 1 (HIV-1) Tat transactivator to promote transcriptional elongation from the HIV-1 long terminal repeat (LTR). Here we exploit fluorescence resonance energy transfer (FRET) to demonstrate that cyclin T1 physically interacts in vivo with the promyelocytic leukaemia (PML) protein within specific subnuclear compartments that are coincident with PML nuclear bodies. Deletion mutants at the C-terminal region of cyclin T1 are negative for FRET with PML and fail to localize to nuclear bodies. Cyclin T1 and PML are also found associated outside of nuclear bodies, and both proteins are present at the chromatinized HIV-1 LTR promoter upon Tat transactivation. Taken together these results suggest that PML proteins regulate Tat- mediated transcriptional activation by modulating the availability of cyclin T1 and other essential cofactors to the transcription machinery.
Marcello
Alessandro
A
Molecular Medicine Laboratory, International Centre for Genetic Engineering and Biotechnology (ICGEB), Area Science Park, Padriciano 99, 34012 Trieste, Italy. marcello@icgeb.org
Ferrari
Aldo
A
Pellegrini
Vittorio
V
Pegoraro
Gianluca
G
Lusic
Marina
M
Beltram
Fabio
F
Giacca
Mauro
M
D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D056906:Cyclin T; D016213:Cyclins / Q000737:chemistry / Q000378:metabolism*; D004735:Energy Transfer; D005453:Fluorescence; D005455:Fluorescent Antibody Technique; D006801:Humans; D009363:Neoplasm Proteins / Q000378:metabolism*; D009687:Nuclear Proteins; D011233:Precipitin Tests; D000071156:Promyelocytic Leukemia Protein; D011485:Protein Binding; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017384:Sequence Deletion; D014157:Transcription Factors / Q000378:metabolism*; D025521:Tumor Suppressor Proteins
C503684:CCNT1 protein, human; D056906:Cyclin T; D016213:Cyclins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human