Prokaryotic transcription occurs in the cytoplasm alongside translation. Organelles. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ...

Initiation

The following steps occur, in order, for transcription initiation:

• RNA polymerase (RNAP) recognizes and specifically binds to the promoter region on DNA. At this stage, the DNA is double-stranded ("closed"). This RNAP/wound-DNA structure is referred to as the closed complex.
• The DNA is unwound and becomes single-stranded ("open") in the vicinity of the initiation site (defined as +1). This RNAP/unwound-DNA structure is called the open complex.
• The RNA polymerase transcribes the DNA, but produces about 10 abortive (short, non-productive) transcripts which are unable to leave the RNA polymerase because the exit channel is blocked by the σ-factor.
• The σ-factor eventually dissociates from the holoenzyme, and elongation proceeds.

Promoters can differ in "strength"; that is, how actively they promote transcription of their adjacent DNA sequence. Promoter strength is in many (but not all) cases, a matter of how tightly RNA polymerase and its associated accessory proteins bind to their respective DNA sequences. The more similar the sequences are to a consensus sequence, the stronger the binding is. The enzyme RNA polymerase or RNAP is a nucleotidyltransferase that polymerises ribonucleotides in accordance with the information present in DNA. RNA polymerase enzymes are essential and are found in all cells of all organisms. ... A promoter is a DNA sequence that contains the information, in the form of DNA sequences, that permits the proper activation or repression of the gene which it controls, i. ... Sigma factor (σ factor) is a prokaryotic initiation factor that binds to RNA polymerase and promotes attachment to promoter sites on DNA. There are seven different sigma factors for different kinds of promoters. ... In biochemistry, holoenzyme may refer either to the complete and operative form of an enzyme with multiple protein subunits or to the combination of an apoenzyme with its cofactor. ... In molecular biology and bioinformatics, a consensus sequence is a way of representing the results of a multiple sequence alignment, where related seqeunces are compared to each other, and similar functional sequence motifs are found. ...

Most transcripts originate using adenosine-5'-triphosphate (ATP) and, to a lesser extent, guanosine-5'-triphosphate (GTP) (purine nucleoside triphosphates) at the +1 site. Uridine-5'-triphosphate (UTP) and cytidine-5'-triphosphate (CTP) (pyrimidine nucleoside triphosphates) are disfavoured at the initiation site. Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Guanosine triphosphate (GTP) is also known as guanosine-5-triphosphate. ... Purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. ... Uridine 5-triphosphate is uridine esterified with triphosphoric acid at its 5-position. ... Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring [1]. It is isomeric with two other forms of diazine. ...

Termination

Two termination mechanisms are well known:

• Intrinsic termination (also called Rho-independent termination) involves terminator sequences within the RNA that signal the RNA polymerase to stop. The terminator sequence is usually a palindromic sequence that forms a stem-loop hairpin structure that leads to the dissociation of the RNAP from the DNA template. One such common termination motif is the palindromic sequence 'GCCGCCG'. The RNA polymerase fails to proceed beyond this point and consequently, the nascent DNA-RNA hybrid dissociates. The RNA polymerase then proceeds to look for a new initiation-region from which to start the initiation process again.
• Rho-dependent termination uses a termination factor called ρ factor(rho factor) to stop RNA synthesis at specific sites. This protein binds and runs along the mRNA towards the RNAP. When ρ-factor reaches the RNAP, it causes RNAP to dissociate from the DNA, terminating transcription.

Other termination mechanisms include where RNAP comes across a region with repetitious thymidine residues in the DNA template, or where a GC-rich inverted repeat followed by 4 A residues. The inverted repeat forms a stable stem loop structure in the RNA, which causes the RNA to dissociate from the DNA template. see also Alexadrome For the movie, see Palindromes (film) Look up Palindrome in Wiktionary, the free dictionary. ... There are other meanings of hairpin In genetics, a hairpin is a part of single-stranded DNA, usually a palindromic sequence, that aligns with itself to form a needle-like structure. ... This article may be too technical for most readers to understand. ... A ρ factor (rho factor) is a protein found in prokaryotes, especially E. coli, involved in the termination of transcription. ...

The -35 region and the -10 ("Pribnow box") region comprise the basic prokaryotic promoter, and |T| stands for the terminator. The DNA on the template strand between the +1 site and the terminator is transcribed into RNA, which is then translated into protein.. The Pribnow box (also known as the Pribnow-Schaller box) is the sequence TATAAT of six nucleotides (thymine-adenine-thymine-etc. ... A promoter is a DNA sequence that contains the information, in the form of DNA sequences, that permits the proper activation or repression of the gene which it controls, i. ... In genetics, a terminator marks the end of a gene on the DNA for transcription. ... Translation is the second process of protein biosynthesis (part of the overall process of gene expression). ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...