title: Identification and biochemical characterization of a novel transcription elongation factor, Elongin A3.
abstract: The Elongin complex stimulates the rate of transcription elongation by RNA polymerase II by suppressing the transient pausing of the polymerase at many sites along the DNA template. Elongin is composed of a transcriptionally active A subunit and two small regulatory B and C subunits, the latter binding stably to each other to form a binary complex that interacts with Elongin A and strongly induces its transcriptional activity. To further understand the role of Elongin A in transcriptional regulation by RNA polymerase II, we are attempting to identify Elongin A-related proteins. Here, we report on the molecular cloning, expression, and biochemical characterization of human Elongin A3, a novel transcription elongation factor that exhibits 49 and 81% identity to Elongin A and the recently identified Elongin A2, respectively. The mRNA of Elongin A3 is ubiquitously expressed, and the protein is localized to the nucleus of cells. Mechanistic studies have demonstrated that Elongin A3 possesses similar biochemical features to Elongin A2. Both stimulate the rate of transcription elongation by RNA polymerase II and are capable of forming a stable complex with Elongin BC. In contrast to Elongin A, however, their transcriptional activities are not activated by Elongin BC. Structure-function analyses using fusion proteins composed of Elongin A3 and Elongin A revealed that the COOH-terminal region of Elongin A is important for the activation by Elongin BC.
authors: Department of Biochemical Genetics, Medical Research Institute, Tokyo Medical and Dental University, 1-5-45, Yushima, Bunkyo-ku, Tokyo 113-8510, Japan.
authors: Katsuhisa
authors: K
authors: Yamazaki
authors: Limei
authors: L
authors: Guo
authors: Kazunori
authors: K
authors: Sugahara
authors: Chun
authors: C
authors: Zhang
authors: Hideaki
authors: H
authors: Enzan
authors: Yusaku
authors: Y
authors: Nakabeppu
authors: Shigetaka
authors: S
authors: Kitajima
authors: Teijiro
authors: T
authors: Aso
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D003001:Cloning, Molecular; D000075065:Elongin; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012319:RNA Polymerase II / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D014157:Transcription Factors / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism
chemical_list: C000616397:ELOA protein, human; C000616398:ELOA2 protein, human; C000616399:ELOA3P pseudogene, human; C000616403:Eloa protein, mouse; D000075065:Elongin; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; D012319:RNA Polymerase II