Terminator (genetics)
Encyclopedia
In genetics, a terminator, or transcription terminator is a section of genetic sequence that marks the end of gene
or operon
on genomic DNA
for transcription
.
In prokaryotes, two classes of transcription terminators are known:
In eukaryotes, terminators are recognized by protein factors
Gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...
or operon
Operon
In genetics, an operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single regulatory signal or promoter. The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo trans-splicing to create...
on genomic DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
for transcription
Transcription (genetics)
Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...
.
In prokaryotes, two classes of transcription terminators are known:
- Intrinsic transcription terminatorsIntrinsic terminationIntrinsic termination is a mechanism in prokaryotes that causes mRNA transcription to be stopped. In this mechanism, the mRNA contains a sequence that can base pair with itself to form a stem-loop structure 7-20 base pairs in length that is also rich in cytosine-guanine base pairs...
where a hairpin structure forms within the nascent transcript that disrupts the mRNA-DNA-RNA polymerase ternary complexPolymeraseA polymerase is an enzyme whose central function is associated with polymers of nucleic acids such as RNA and DNA.The primary function of a polymerase is the polymerization of new DNA or RNA against an existing DNA or RNA template in the processes of replication and transcription...
. - Rho-dependent transcription terminators that require Rho factorRho factorA ρ factor is a prokaryotic protein involved in the termination of transcription.Rho factor is an essential transcription protein in prokaryotes. In Escherichia coli, it is a ~275 kD hexamer of identical subunits. Each subunit has an RNA-binding domain and an ATP-hydrolysis domain...
, an RNA helicaseHelicaseHelicases are a class of enzymes vital to all living organisms. They are motor proteins that move directionally along a nucleic acid phosphodiester backbone, separating two annealed nucleic acid strands using energy derived from ATP hydrolysis.-Function:Many cellular processes Helicases are a...
protein complex, to disrupt the nascent mRNA-DNA-RNA polymerase ternary complex.
In eukaryotes, terminators are recognized by protein factors