title: New insights into the control of HIV-1 transcription: when Tat meets the 7SK snRNP and super elongation complex (SEC).
abstract: Recent studies aimed at elucidating the mechanism controlling HIV-1 transcription have led to the identification and characterization of two multi-subunit complexes that both contain P-TEFb, a human transcription elongation factor and co-factor for activation of HIV-1 gene expression by the viral Tat protein. The first complex, termed the 7SK snRNP, acts as a reservoir where active P-TEFb can be withdrawn by Tat to stimulate HIV-1 transcription. The second complex, termed the super elongation complex (SEC), represents the form of P-TEFb delivered by Tat to the paused RNA polymerase II at the viral long terminal repeat during Tat transactivation. Besides P-TEFb, SEC also contains other elongation factors/co-activators, and they cooperatively stimulate HIV-1 transcription. Recent data also indicate SEC as a target for the mixed lineage leukemia (MLL) protein to promote the expression of MLL target genes and leukemogenesis. Given their roles in HIV-1/AIDS and cancer, further characterization of 7SK snRNP and SEC will help develop strategies to suppress aberrant transcriptional elongation caused by uncontrolled P-TEFb activation. As both complexes are also important for normal cellular gene expression, studying their structures and functions will elucidate the mechanisms that control metazoan transcriptional elongation in general.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA.
authors.forename: Nanhai
authors.initials: N
authors.lastname: He
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhou
mesh_terms: D000818:Animals; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D042925:Positive Transcriptional Elongation Factor B / Q000235:genetics* / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000235:genetics* / Q000378:metabolism
chemical_list: D017411:Ribonucleoproteins, Small Nuclear; D054322:tat Gene Products, Human Immunodeficiency Virus; D042925:Positive Transcriptional Elongation Factor B