title: Domains in the SPT5 protein that modulate its transcriptional regulatory properties.
abstract: SPT5 and its binding partner SPT4 regulate transcriptional elongation by RNA polymerase II. SPT4 and SPT5 are involved in both 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB)-mediated transcriptional inhibition and the activation of transcriptional elongation by the human immunodeficiency virus type 1 (HIV-1) Tat protein. Recent data suggest that P-TEFb, which is composed of CDK9 and cyclin T1, is also critical in regulating transcriptional elongation by SPT4 and SPT5. In this study, we analyze the domains of SPT5 that regulate transcriptional elongation in the presence of either DRB or the HIV-1 Tat protein. We demonstrate that SPT5 domains that bind SPT4 and RNA polymerase II, in addition to a region in the C terminus of SPT5 that contains multiple heptad repeats and is designated CTR1, are critical for in vitro transcriptional repression by DRB and activation by the Tat protein. Furthermore, the SPT5 CTR1 domain is a substrate for P-TEFb phosphorylation. These results suggest that C-terminal repeats in SPT5, like those in the RNA polymerase II C-terminal domain, are sites for P-TEFb phosphorylation and function in modulating its transcriptional elongation properties.
authors.affiliation: Division of Hematology-Oncology, Department of Medicine, Harold Simmons Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas 75235-8594, USA.
authors.forename: D
authors.initials: D
authors.lastname: Ivanov
authors.forename: Y T
authors.initials: YT
authors.lastname: Kwak
authors.forename: J
authors.initials: J
authors.lastname: Guo
authors.forename: R B
authors.initials: RB
authors.lastname: Gaynor
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases / Q000378:metabolism; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D015696:Gene Products, tat / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D042925:Positive Transcriptional Elongation Factor B; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D012319:RNA Polymerase II / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid; D014158:Transcription, Genetic; D035602:Transcriptional Elongation Factors
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D015696:Gene Products, tat; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C080991:SPT4 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D035602:Transcriptional Elongation Factors; C069940:SPT5 transcriptional elongation factor; D004004:Dichlororibofuranosylbenzimidazole; D042925:Positive Transcriptional Elongation Factor B; D017346:Protein Serine-Threonine Kinases; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9; D018844:Cyclin-Dependent Kinases; D012319:RNA Polymerase II