5S ribosomal RNA
5S ribosomal RNA (5S

Svedberg

A svedberg is a non-SI physical unit used for sedimentation coefficients.  It characterizes the behaviour of a particle type in sedimentation processes, notably centrifugation.  The svedberg is technically a measure of time, and is defined as exactly 10-13 seconds A svedberg (symbol S, sometimes...

 rRNA) is a component of the large ribosomal

Ribosome

A ribosome is a component of cells that assembles the twenty specific amino acid molecules to form the particular protein molecule determined by the nucleotide sequence of an RNA molecule....

 subunit in both prokaryote

Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other membrane-bound organelles. The organisms that have a cell nucleus are called eukaryotes. Most prokaryotes are unicellular, but a few such as myxobacteria have multicellular stages in their life cycles...

s (50S

50S

50S is the larger subunit of the 70S ribosome of prokaryotes. It is the site of inhibition for antibiotics such as macrolides, chloramphenicol, clindamycin, and the pleuromutilins. It includes the subunits 5S and 23S.-Structure:...

) and eukaryote

Eukaryote

A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

s (60S

60S

60S is the large ribosomal subunit in eukaryotes. It corresponds to 50S in prokaryotes.It consists of the following:* 5S* 28S* 5.8SThe following is a list of proteins contained within the 60S ribosome:...

).

Eukaryotic 5S rRNA is synthesised by RNA polymerase III

RNA polymerase III

RNA polymerase III transcribes DNA to synthesize ribosomal 5S rRNA, tRNA and other small RNAs. The genes transcribed by RNA Pol III fall in the category of "housekeeping" genes whose expression is required in all cell types and most environmental conditions...

, whereas most other eukaroytic rRNAs are cleaved from a 45S precursor transcribed by RNA polymerase I

RNA polymerase I

RNA polymerase I is, in eukaryotes, the enzyme that only transcribes ribosomal RNA , a type of RNA that accounts for over 50% of the total RNA synthesized in a cell....

. In Xenopus

Xenopus

Xenopus is a genus of highly aquatic frogs native to Sub-Saharan Africa. There are 19 species in the Xenopus genus...

oocyte

Oocyte

An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...

s, it has been shown that fingers 4-7 of the nine-zinc finger

Zinc finger

Zinc fingers are small protein structural motifs that can coordinate one or more zinc ions to help stabilize their folds. They can be classified into several different structural families and typically function as interaction modules that bind DNA, RNA, proteins, or small molecules...

 transcription factor

Transcription factor

In molecular biology and genetics, a transcription factor is a protein that binds to specific DNA sequences, thereby controlling the flow of genetic information from DNA to mRNA...

 TFIIIA can bind to the central region of 5S RNA. Binding between 5S rRNA and TFIIIA serves to both repress further 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...

 of the 5S RNA gene

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...

and stabilize the 5S RNA transcript until it is required for ribosome assembly.