Drosophila roX RNA
Encyclopedia
RoX RNA is a non-coding RNA
(ncRNA) present in the male-specific lethal (MSL) complex and is required for sex dosage compensation
in Drosophila
. As males only contain one X chromosome
, male flies dosage compensate for the X chromosome by hyper-transcribing the X chromosome. This is achieved by the MSL complex binding to the X chromosome and inducing histone
H4 lysine 16 acetylation
and allows for the formation of euchromatin
. These ncRNAs were first discovered in RNA extracted from neuronal cells.
Two roX RNAs have been identified in the MSL complex from Drosophila melanogaster
and have been shown to be conserved across different drosophila species. The two roX RNAs, known as roX1 and roX2 have been shown to differ in primary sequence and sequence length but despite these differences they both contain a MSL binding site are functionally redundant. Cloning
roX genes and subsequent sequence alignment
from a number of different drosophila species identified several conserved regions and it was also noticed that roX RNA is only present in male flies.
Secondary structure
predictions predicted a stem loop to be present at the 3' end of the roX RNA transcripts. Mutagenesis
within this region that either altered the sequence or prevented stem loop formation was shown to be lethal in male flies as they were unable to dosage compensate as these mutations prevented MSL binding to the X chromosome. It was also shown that in the presence of mutant
roX RNA the MSL complex was unable to localize on the X chromosome and mislocalize to the heterochromatic chromocenter. This suggests that roX RNA plays a role in directing MSL complex to the X chromosome. Sequence alignment
of roX2 identified several regions of sequence conservation known as Gub regions and are absent in roX1. Many of these Gub regions are though to be redundant as mutating has no effect however, Gub1 which is present within the 3' stem loop region is thought to be a key motif required for roX2 as Gub1 mutations were shown to be lethal. These studies show that roX RNA are essential for dosage compensation where that the 3' stem loop region in the roX RNA are crucial for MSL localization and it is thought to be the motif that allows the two roX RNAs to be functionally redundant.
Non-coding RNA
A non-coding RNA is a functional RNA molecule that is not translated into a protein. Less-frequently used synonyms are non-protein-coding RNA , non-messenger RNA and functional RNA . The term small RNA is often used for short bacterial ncRNAs...
(ncRNA) present in the male-specific lethal (MSL) complex and is required for sex dosage compensation
Dosage compensation
Dosage compensation, also known as Ohno's Hypothesis, is a hypothetical genetic regulatory mechanism which operates to equalize the phenotypic expression of characteristics determined by genes on the X chromosome so that they are equally expressed in the human XY male and the XX female. In 2006,...
in Drosophila
Drosophila
Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...
. As males only contain one X chromosome
X chromosome
The X chromosome is one of the two sex-determining chromosomes in many animal species, including mammals and is common in both males and females. It is a part of the XY sex-determination system and X0 sex-determination system...
, male flies dosage compensate for the X chromosome by hyper-transcribing the X chromosome. This is achieved by the MSL complex binding to the X chromosome and inducing histone
Histone
In biology, histones are highly alkaline proteins found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and play a role in gene regulation...
H4 lysine 16 acetylation
Acetylation
Acetylation describes a reaction that introduces an acetyl functional group into a chemical compound...
and allows for the formation of euchromatin
Euchromatin
Euchromatin is a lightly packed form of chromatin that is rich in gene concentration, and is often under active transcription. Unlike heterochromatin, it is found in both cells with nuclei and cells without nuclei...
. These ncRNAs were first discovered in RNA extracted from neuronal cells.
Two roX RNAs have been identified in the MSL complex from Drosophila melanogaster
Drosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...
and have been shown to be conserved across different drosophila species. The two roX RNAs, known as roX1 and roX2 have been shown to differ in primary sequence and sequence length but despite these differences they both contain a MSL binding site are functionally redundant. Cloning
Cloning
Cloning in biology is the process of producing similar populations of genetically identical individuals that occurs in nature when organisms such as bacteria, insects or plants reproduce asexually. Cloning in biotechnology refers to processes used to create copies of DNA fragments , cells , or...
roX genes and subsequent sequence alignment
Sequence alignment
In bioinformatics, a sequence alignment is a way of arranging the sequences of DNA, RNA, or protein to identify regions of similarity that may be a consequence of functional, structural, or evolutionary relationships between the sequences. Aligned sequences of nucleotide or amino acid residues are...
from a number of different drosophila species identified several conserved regions and it was also noticed that roX RNA is only present in male flies.
Secondary structure
Secondary structure
In biochemistry and structural biology, secondary structure is the general three-dimensional form of local segments of biopolymers such as proteins and nucleic acids...
predictions predicted a stem loop to be present at the 3' end of the roX RNA transcripts. Mutagenesis
Mutagenesis
Mutagenesis is a process by which the genetic information of an organism is changed in a stable manner, resulting in a mutation. It may occur spontaneously in nature, or as a result of exposure to mutagens. It can also be achieved experimentally using laboratory procedures...
within this region that either altered the sequence or prevented stem loop formation was shown to be lethal in male flies as they were unable to dosage compensate as these mutations prevented MSL binding to the X chromosome. It was also shown that in the presence of mutant
Mutant
In biology and especially genetics, a mutant is an individual, organism, or new genetic character, arising or resulting from an instance of mutation, which is a base-pair sequence change within the DNA of a gene or chromosome of an organism resulting in the creation of a new character or trait not...
roX RNA the MSL complex was unable to localize on the X chromosome and mislocalize to the heterochromatic chromocenter. This suggests that roX RNA plays a role in directing MSL complex to the X chromosome. Sequence alignment
Sequence alignment
In bioinformatics, a sequence alignment is a way of arranging the sequences of DNA, RNA, or protein to identify regions of similarity that may be a consequence of functional, structural, or evolutionary relationships between the sequences. Aligned sequences of nucleotide or amino acid residues are...
of roX2 identified several regions of sequence conservation known as Gub regions and are absent in roX1. Many of these Gub regions are though to be redundant as mutating has no effect however, Gub1 which is present within the 3' stem loop region is thought to be a key motif required for roX2 as Gub1 mutations were shown to be lethal. These studies show that roX RNA are essential for dosage compensation where that the 3' stem loop region in the roX RNA are crucial for MSL localization and it is thought to be the motif that allows the two roX RNAs to be functionally redundant.