![]() ![]() 1996), and therefore the DNA sequences recognized by α are also likely to be highly conserved. The αCTD residues most crucial for DNA interaction are nearly invariant in bacteria ( Gaal et al. 1994) and with a number of transcriptional activators ( Igarashi and Ishihama 1991 Busby and Ebright 1994 Savery et al. The 8-kD carboxy-terminal domain (αCTD) is responsible for interaction with the UP element ( Blatter et al. The 28-kD amino-terminal domain (αNTD) is responsible for dimerization of α and for interaction with the remainder of RNAP ( Igarashi and Ishihama 1991 Busby and Ebright 1994). 1995).Įach RNAP α subunit consists of two domains connected by a long unstructured and/or flexible linker ( Blatter et al. UP elements have been identified upstream of many bacterial and phage promoters and can function with RNAPs containing different ς factors (e.g., Newlands et al. A consensus UP element sequence (referred to here as the consensus full UP element), derived from binding-site-selection experiments, consists almost exclusively of A and T residues and increases promoter activity >300-fold ( Estrem et al. 1994), and UP element-α interactions facilitate initial binding of RNAP and subsequent step(s) in transcription initiation ( Rao et al. The best-characterized UP element is in the rrnB P1 promoter, in which the sequence determinants are located between positions −40 and −60 with respect to the transcription start site ( Rao et al. 1992), and the UP element, located upstream of the −35 element, is recognized by the RNAP α subunit ( Ross et al. The −10 and −35 elements are recognized by the RNAP ς subunit ( Dombroski et al. We propose that each subsite constitutes a binding site for a copy of αCTD, and that binding of an αCTD to the proximal subsite region (through specific interactions with a consensus proximal subsite or through nonspecific interactions with a nonconsensus proximal subsite) is a prerequisite for binding of the other αCTD to the distal subsite.īacterial promoters consist of at least three RNA polymerase (RNAP) recognition sequences: The −10 element, the −35 element, and the UP element ( Hawley and McClure 1983 Ross et al. Furthermore, function of the consensus proximal subsite requires only one copy of αCTD, whereas function of the consensus distal subsite requires both copies of αCTD. The selected proximal subsites (positions −46 to −38 consensus 5′-AAAAAARNR-3′) stimulate transcription up to 170-fold, and the selected distal subsites (positions −57 to −47 consensus 5′-AExperiments with RNAP derivatives containing only one copy of αCTD indicate, in contrast to a previous report, that the two αCTDs function interchangeably with respect to UP element recognition. Using binding-site-selection experiments, we identify the consensus sequence for each subsite. ![]() We demonstrate here that the previously described bacterial promoter upstream element (UP element) consists of two distinct subsites, each of which, by itself, can bind the RNA polymerase holoenzyme α subunit carboxy-terminal domain (RNAP αCTD) and stimulate transcription. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |