Maize Transposable Elements: Structure, Function, and Regulation
We have mapped a transcript of the maize transposable element Ac. Virtually the entire 4.5-kb Ac element is transcribed as a single RNA molecule from which four introns are spliced to yield a 3.5-kb mRNA. The Ac mRNA codes for an 807 amino acid protein, which is presumably the transposase. The Ac element can be reversibly inactivated by methylation of the promoter and 5′ untranscribed leader region to convert the Ac element to a Ds-like element.
The Ac element can support the transposition both of itself and of a number of types of Ds elements. The Ds elements have the same terminal inverted repeats as does Ac, and also are associated with the characteristic 8-bp duplication of host DNA at the site of insertion. The Ds1 element, which was first isolated from the Adh1-Fm335 allele, is a 405-bp segment and is repeated 40–50 times in the genomes of all maize lines, and in the maize relatives Teosinte and Tripsacum. The Ds1 element generates an additional intron in the Adh1-Fm335 allele; all but 14 bp of the element are spliced from the Adh1 mRNA.
KeywordsTransposable Element Inverted Repeat Transposable Element Activator Maize Transposable Element Adh1 mRNA
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