Analysis of the 24 genomic FB insertions shows that 58.3% of the FB elements insert into intronic sequences, 37.5% insert 5' to genes and 4.2% insert in a gene downstream region. FB elements have a consensus structure: each begins with a 470bp of non-repetitive sequence followed by a set of 154bp blocks. Each block starts with the sequence CTC and is composed of five almost identical repeats of 32bp. When NOF elements are present within FB elements, they are always found after the sequence TCCT in the second repeat of a block. It is possible that the composite FB-NOF is the complete transposable element.
Ectopic recombination occurs between two FB elements, recombination involves partial loss of the FB sequence. this can be explained by recombination mediated by the long terminal repeat sequences of the FB element.
The distribution of FB and NOF sequences in a number of different strains has been studied. NOF sequences are almost invariably associated with FB element sequences.
First described as elements containing inverted repeat sequences (Potter et al., 1980). The inverted repeats at the ends of FB elements vary in length; they are made up of different numbers of tandemly repeated sequences, with a maximum repeat length of 155 base pairs (Truett, Jones and Potter, 1981; Potter, 1982). The DNA between the inverted repeats also varies. The element FB4 has been sequenced entirely (Potter, 1982). Its restriction map and terminal sequences are shown. The only HinfI and TaqI sites marked, are those that lie in the inverted repeats. There are no sites for the enzymes AvaI, BamHI, EcoRI, HpaI, PstI, SacI, SalI, SmaI, or XhoI. Potter (1982) has suggested that another transposable element, HB1, lies between coordinates 1.1 and 2.75 of FB4. The sequence of the central region of an FB element related to FB-wc, the element responsible for the wc mutation, has been determined (Templeton and Potter, 1989). It contains two long open reading frames in one strand and these authors suggest that they may encode functions required for transposition of FB elements. They have evidence that the product of the first open reading frame is a 71kD polypeptide present in early embryos and egg chambers. FB elements have been found at the ends of the TE elements (Ising and Ramel, 1976; Paro, Golberg and Gehring, 1983). The smallest known element of this type is associated with the mutation wDZL (Levis and Rubin, 1982).
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External Crossreferences and Linkouts ( 16 )
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GenBank Nucleotide
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A collection of sequences from several sources, including GenBank, RefSeq, TPA, and PDB.
Analysis of the 24 genomic FB insertions shows that 58.3% of the FB elements insert into intronic sequences, 37.5% insert 5' to genes and 4.2% insert in a gene downstream region. FB elements have a consensus structure: each begins with a 470bp of non-repetitive sequence followed by a set of 154bp blocks. Each block starts with the sequence CTC and is composed of five almost identical repeats of 32bp. When NOF elements are present within FB elements, they are always found after the sequence TCCT in the second repeat of a block. It is possible that the composite FB-NOF is the complete transposable element.
The direct duplications are strongly A/T rich, except for the first position, which is C/G in 71% of the studied sequences.
The distribution of FB elements in heterochromatin has been studied by in situ hybridisation to mitotic chromosomes.
Ectopic recombination occurs between two FB elements, recombination involves partial loss of the FB sequence. this can be explained by recombination mediated by the long terminal repeat sequences of the FB element.
The distribution of FB and NOF sequences in a number of different strains has been studied. NOF sequences are almost invariably associated with FB element sequences.
Complete FB transposable elements encode a novel protein found in D.melanogaster.
A number of chromosomal rearrangements induced by FB elements have been studied.
FB-NOF (Nofretete) has a large, characteristic internal segment of 4.5kb.
First described as elements containing inverted repeat sequences (Potter et al., 1980). The inverted repeats at the ends of FB elements vary in length; they are made up of different numbers of tandemly repeated sequences, with a maximum repeat length of 155 base pairs (Truett, Jones and Potter, 1981; Potter, 1982). The DNA between the inverted repeats also varies. The element FB4 has been sequenced entirely (Potter, 1982). Its restriction map and terminal sequences are shown. The only HinfI and TaqI sites marked, are those that lie in the inverted repeats. There are no sites for the enzymes AvaI, BamHI, EcoRI, HpaI, PstI, SacI, SalI, SmaI, or XhoI. Potter (1982) has suggested that another transposable element, HB1, lies between coordinates 1.1 and 2.75 of FB4. The sequence of the central region of an FB element related to FB-wc, the element responsible for the wc mutation, has been determined (Templeton and Potter, 1989). It contains two long open reading frames in one strand and these authors suggest that they may encode functions required for transposition of FB elements. They have evidence that the product of the first open reading frame is a 71kD polypeptide present in early embryos and egg chambers. FB elements have been found at the ends of the TE elements (Ising and Ramel, 1976; Paro, Golberg and Gehring, 1983). The smallest known element of this type is associated with the mutation wDZL (Levis and Rubin, 1982).