[mage lang=”en|es|fr|en” source=”flickr”]telomerase rna component[/mage]
Does the nucleolus have other functions, apart from production of ribosomes?
On wikipedia it says “Additionally, recent research pointed out that the nucleolus is also responsible for the trafficking of various prominent small RNA species. The nucleolus helps them during their maturation process and route to their final cellular destination. Moreover, although nucleoli become invisible during cell division, more recent studies have found that they are involved in cell cycle regulation. Several of its non-traditional roles include interaction with viral components, the regulation of tumor suppressor and oncogene activities, signal recognition particle assembly, the modification of small RNA strands, the control of aging and modulating telomerase function.”
I don’t know what this means. Can anyone explain?
How much detail do you need?
“Additionally, recent research pointed out that the nucleolus is also responsible for the trafficking of various prominent small RNA species.”
In addition to the commonly known classes of RNA (rRNA, tRNA and mRNAs) there are other important RNAs in cells, many of which are transcribed, processed or pass through the nucleolus. These include snoRNAs, snRNAs, telomerase RNA, 5S rRNA, RNAse P RNA, 7SL RNA and miRNAs.
“…recent studies have found that they are involved in cell cycle regulation.”
Many different proteins are found in the nucleolus at differen times of the cell cycle. It could be that by changing what proteins are bound in the nucleolus and what proteins are released are important for making sure the cell cycle proceeds correctly.
“…non-traditional roles include interaction with viral components,”
Some of the proteins in viruses need to be in the nucleolus for the virus to replicate.
“…the regulation of tumor suppressor and oncogene activities,”
Among the many proteins that can be found in the nucleolus are proteins that are involved in DNA repair. Mutations in these nucleolar proteins care frequently found in some types of cancer.
“signal recognition particle assembly”
The SRP is made up of proteins and RNA. SRP proteins and SPR RNA pass through the nucleolus before being exported from the nucleus to the cytosol. This suggest that something happens to the SRP in the nucleolus.
“the modification of small RNA strands”
Many modifications are made to RNAs before they become functional. These include addition of a methyl group to the 2′ OH of ribose and altering the base attached to the sugar backbone. Some modified bases are pseudouridine and inosine.
“…the control of aging and modulating telomerase function.”
Telomerase is an enzyme that lengthens the telomeres of chromosomes. This enzyme is made up of proteins and RNA. The RNA is used as a template to reverse-transcribe the correct DNA sequence of telomeres. Telomerase is found in the nucleolus and released late in S phase of the cycle to replicate telomeres.
The end replication problem of linear chromosomes are what is thought to limit how many times a cell can divide. Telomeres are repetitive DNA sequences that protect the ends of chromosomes. With each cell division telomeres get shorter. Once telomeres are lost, cells can’t divide without losing DNA or having exposed, unprotected ends of chromosomes leading to chromosomal rearrangement. It is thought that longevity is limited by telomere length which limits how many times a cell can divide.
Only certain cells have telomerase enzyme at all. One of the frequent mutations found in cancer is reactivation of telomerase in cells which should not have it turned on.
Houdini PRO at TERC International