SINEs[edit source |
editbeta]
Short INterspersed Elements[9] are short DNA sequences (<500 bases[17]) that
represent reverse-transcribed RNA molecules originally transcribed by RNA polymerase III
into tRNA, 5S ribosomal RNA,
and other small nuclear RNAs. SINEs do not encode a functional reverse
transcriptase protein and rely on other mobile elements for transposition. The
most common SINEs in primates are called Alu sequences. Alu
elements are approximately 350 base pairs long, do not contain any coding
sequences, and can be recognized by the restriction
enzyme AluI (hence the name). With about
1,500,000 copies, SINEs make up about 11% of the human genome.[13] While
historically viewed as "junk DNA", recent research suggests that, in some rare
cases, both LINEs and SINEs were incorporated into novel genes so as to evolve
new functionality.[18] The
distribution of these elements has been implicated in some genetic diseases and
cancers. Although sequence analysis of human Alu subfamilies shows the existence
of mosaic (recombinant) elements, experimental evidence is lacking. In the
primitive eukaryote Entamoeba histolytica, the frequent exchange of
sequence during retrotransposition has been reported; this results in a mosaic
pattern in its SINE sequences.[19]
Composite SINE Transposons[edit source |
editbeta]
Two SINEs may act in concert to flank and mobilize an
intervening single copy DNA sequence. This was reported for a 710 bp DNA
sequence upstream of the bovine beta globin gene.[20] The DNA
arrangement forms a composite transposon whose presence has been confirmed by
the complete bovine genomic sequence
where the mobilized sequence may be found on bovine chromosome 15 in contig
NW_001493315.1
nucleotides #1085432–1086142 and the originating sequence may be found on bovine
chromosome 2 in contig NW_001501789.2
nucleotides #1096679–1097389. It is likely that similar composite transposons
exist in other bovine genomic regions and other mammalian genomes. They could be
detected with suitable algorithms.
editbeta]
Short INterspersed Elements[9] are short DNA sequences (<500 bases[17]) that
represent reverse-transcribed RNA molecules originally transcribed by RNA polymerase III
into tRNA, 5S ribosomal RNA,
and other small nuclear RNAs. SINEs do not encode a functional reverse
transcriptase protein and rely on other mobile elements for transposition. The
most common SINEs in primates are called Alu sequences. Alu
elements are approximately 350 base pairs long, do not contain any coding
sequences, and can be recognized by the restriction
enzyme AluI (hence the name). With about
1,500,000 copies, SINEs make up about 11% of the human genome.[13] While
historically viewed as "junk DNA", recent research suggests that, in some rare
cases, both LINEs and SINEs were incorporated into novel genes so as to evolve
new functionality.[18] The
distribution of these elements has been implicated in some genetic diseases and
cancers. Although sequence analysis of human Alu subfamilies shows the existence
of mosaic (recombinant) elements, experimental evidence is lacking. In the
primitive eukaryote Entamoeba histolytica, the frequent exchange of
sequence during retrotransposition has been reported; this results in a mosaic
pattern in its SINE sequences.[19]
Composite SINE Transposons[edit source |
editbeta]
Two SINEs may act in concert to flank and mobilize an
intervening single copy DNA sequence. This was reported for a 710 bp DNA
sequence upstream of the bovine beta globin gene.[20] The DNA
arrangement forms a composite transposon whose presence has been confirmed by
the complete bovine genomic sequence
where the mobilized sequence may be found on bovine chromosome 15 in contig
NW_001493315.1
nucleotides #1085432–1086142 and the originating sequence may be found on bovine
chromosome 2 in contig NW_001501789.2
nucleotides #1096679–1097389. It is likely that similar composite transposons
exist in other bovine genomic regions and other mammalian genomes. They could be
detected with suitable algorithms.