Plant-transposable elements and gene tagging.
Explore the source record for details and available documents.
Base Sequence↗
Biomedical subjects
A Gierl
Publications and source records attributed to A Gierl.
Molecular analysis of the Ubiquitous (Uq) transposable element system of Zea mays.
The Uq transposable element of maize is the most widely dispersed among different maize populations and genetic testerstrains. Despite intensive genetic characterization, little is known about its molecular structure. In order to obtain information relevant to this topic, we have cloned and sequenced three ruq receptors. Surprisingly, they are all Ds1-like receptor types of the Ac-Ds transposon family. Based on our molecular data, we present a model to explain the functional differences associated with the differential expression of the Uq and Ac transposon systems.
Base Sequence↗
Eukaryotic transposable elements with short terminal inverted repeats.
Transposable elements with short terminal inverted repeats are believed to transpose directly from DNA to DNA via excision and integration. The cis/trans requirements for transposition have recently been characterized for some of these elements. Common features seem to emerge for the mechanisms of excision of these elements, with the mechanisms apparently similar for the different elements.
Animals↗
En/Spm encoded tnpA protein requires a specific target sequence for suppression.
The En/Spm encoded suppressor function has been reconstituted in transgenic tobacco protoplasts. The suppressor affects genes which contain an En/Spm responsive transposable element in the transcribed sequences. The En/Spm encoded protein tnpA binds a defined cis element in the inserted transposon, repressing expression of the adjacent gene. This was shown by monitoring transient expression of a bacterial marker gene (GUS) expressed from a strong plant viral promoter. Suppressible variants of the marker gene were produced by inserting I element sequences into the untranslated sequences of the GUS transcript. Comparison of transient expression of these variants in wildtype tobacco protoplasts with their expression in protoplasts transgenic for tnpA protein demonstrates that tnpA is the suppressor. In addition, the minimal cis element required for suppression has been defined as a dimer consisting of two 12 bp tnpA binding sequences in a particular inverted orientation. One of these dimers occurs in each En/Spm end close to the characteristic 13 bp terminal inverted repeat. TnpA binding sites in different arrangements do not respond as well to tnpA. The implications of this observation are discussed. This system can be used to analyse tnpA-DNA interactions involved in gene regulation further.
Alleles↗
The En/Spm transposable element of Zea mays contains splice sites at the termini generating a novel intron from a dSpm element in the A2 gene.
The A2 locus of Zea mays, identified as one of the genes affecting anthocyanin biosynthesis, was cloned using the transposable elements rcy and dSpm as gene tags. The A2 gene encodes a putative protein of 395 amino acids and is devoid of introns. Two a2-m1 alleles, containing dSpm insertions of different sizes, were characterized. The dSpm element from the original state allele has perfect termini and undergoes frequent transposition. The element from the class II state allele is no longer competent to transpose. It has retained the 13 bp terminal inverted repeat but has lost all subterminal sites at the 5' end, which are recognized by tnpA protein, the most abundant product of the En/Spm transposable element system. The relatively high A2 gene expression of one a2-m1 allele is due to removal of almost all dSpm sequences by splicing. The slightly altered A2 enzyme is still functional as shown by complementation of an a2 mutant with the corresponding cDNA. The 5' and 3' splice sites are constituted by the termini of the dSpm element; it therefore represents a novel intron of the A2 gene.
Alleles↗
Excision of the En/Spm transposable element of Zea mays requires two element-encoded proteins.
An excision assay system for En/Spm was developed in transgenic tobacco. The characteristics of excision and integration are similar to the natural system of Zea mays. In this transgenic model system two En/Spm encoded trans-acting functions, TNPA and TNPD, are required for excision. A biochemical model for transposition is proposed that might also be applicable to other transposable elements.
Cloning, Molecular↗
How maize transposable elements escape negative selection.
The transposable element systems En/Spm and Ac affect gene structure and control the expression of genes. In some cases, the deleterious consequences of insertional mutagenesis are reduced because certain members of these families of elements mimic introns. The potential benefits of such interactions, and a multilevel control of transposition activity, might explain 'survival' of these elements during evolution.
Base Sequence↗
The En/Spm transposable element of Zea mays.
Explore the source record for details and available documents.
DNA Transposable Elements↗
Maize transposable elements.
Explore the source record for details and available documents.
DNA Transposable Elements↗
TnpA product encoded by the transposable element En-1 of Zea mays is a DNA binding protein.
TnpA protein, the function encoded by the most abundant transcript of En-1 was expressed in Escherichia coli. DNA binding experiments with partially purified tnpA protein revealed that it binds to the subterminal repetitive region of En-1. TnpA protein recognizes a 12-bp-long sequence motif which is reiterated several times at the termini of En-1. Binding is reduced if the cytosine residues of CG dinucleotides and CNG trinucleotides within the motif are methylated. These data suggest a model in which the product of tnpA serves as a regulator of element activity.
Base Sequence↗