Oryza_sativaFamily: RNA_pol_A_CTD Number of Genes: 1
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The alpha subunit of RNA polymerase consists of two independently folded domains, referred to as amino-terminal and carboxyl terminal domains. The amino terminal domain is involved in the interaction with the other subunits of the RNA polymerase. The carboxyl-terminal domain interacts with the DNA and activators. The amino acid sequence of the alpha subunit is conserved in prokaryotic and chloroplast RNA polymerases. There are three regions of particularly strong conservation, two in the amino-terminal and one in the carboxyl- terminal [2].


The core of the bacterial RNA polymerase (RNAP) consists of four subunits, two alpha, a beta and a beta', which are conserved from bacteria to mammals. The alpha subunit (RpoA) initiates RNAP assembly by dimerising to form a platform on which the beta subunits can interact. The alpha subunit consists of a N-terminal domain (NTD) and a C-terminal domain (CTD), connected by a short linker. The NTD is essential for RNAP assembly, while the CTD is necessary for transcription regulation, interacting with transcription factors and promoter upstream elements. In Escherichia coli, the catabolite activator protein (CAP or CRP) was shown to exert its effect through its interactions with the CTD, where CAP binding to CTD promotes RNAP binding to promoter DNA, thereby stimulating transcription initiation at class I CAP-dependent promoters. At class II CAP-dependent promoters, the interaction of CAP with CTD is one of multiple interactions involved in activation [PUBMED:12202833].


  1. Jeon YH, Negishi T, Shirakawa M, Yamazaki T, Fujita N, Ishihama A, Kyogoku Y; , Science 1995;270:1495-1497.: Solution structure of the activator contact domain of the RNA polymerase alpha subunit. PUBMED:7491496 EPMC:7491496 .

  2. Ebright RH, Busby S; , Curr Opin Genet Dev 1995;5:197-203.: The Escherichia coli RNA polymerase alpha subunit: structure and function. PUBMED:7613089 EPMC:7613089 .

  3. Murakami K, Kimura M, Owens JT, Meares CF, Ishihama A; , Proc Natl Acad Sci USA 1997;94:1709-1714.: The two alpha subunits of Escherichia coli RNA polymerase are asymmetrically arranged and contact different halves of the DNA upstream element. PUBMED:9050843 EPMC:9050843.