encoding plastid RNA polymerase sigma factors in ..
Prokaryotes use two means for terminating transcription, factor-independent and factor-dependent. Certain DNA sequences function as signals that tell the RNA polymerase to terminate transcription. The DNA of a terminator sequence encoded an inverted repeat and an adjacent stretch of uracils. Factor-dependent termination involves a terminator sequence as well as a factor or protein called rho. The mechanisms by which eukaryotes terminate transcription are poorly understood. Most eukaryotic genes are transcribed for up to several thousand base pairs beyond the actual end of the gene. The excess RNA is then cleaved from the transcript when the RNA is processed into its mature form.
(or noncoding strand), is used as a template for RNA synthesis.
RNA pol I promoter consists of a 70 base pair long core element and an upstream element that is about 100 base pairs long. The core spans a segment of DNA that includes sequences that are both up and downstream of the initiation site.
RNA pol III promoters for tRNA are found downstream of the initiation point. These promoters consist of two elements, the first of which is located 8 to 30 base pairs downstream and is called Box A. The second element is 50 to 70 base pairs downstream and is called Box B.
Fibroblast Growth Factors (FGF)
Eukaryotes have four different RNA polymerases (RNA pol). Three are required for transcription of nuclear genes and the fourth for transcription of mitochondrial genes. RNA polymerase I transcribes ribosomal RNA (rRNA), pol II transcribes mRNA and pol III tRNA and several small RNA's. The three polymerases consist of ten or more subunits. All have two large subunits with homology to the and ' subunits of the prokaryotic RNA polymerase. The three eukaryotic polymerases can be distinguished based on their sensitivity to -amanitin, a toxin found in some types of mushrooms. RNA pol II activity is severely inhibited, pol III weakly and pol I is insensitive. The antibiotic rifampicin inhibits prokaryotic RNA polymerases.
Transcription factor - Wikipedia
RNA polymerase links ribonucleotides together in a 5' to 3' direction. The polymerase induces the 3' hydroxyl group of the nucleotide at the 3' end of the growing RNA chain which attacks (nucleophilic) the a phosphorous of the incoming ribonucleotide. A diphosphate is released and the 5' carbon of the incoming nucleotide is linked through a phosphodiester bond to the 3' carbon of the preceding nucleotide.