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Presence of an SAR‐like sequence in junction regions between an introduced transgene and genomic DNA of cultured tobacco cells: its effect on transformation frequency
Author(s) -
Shimizu Katsuya,
Takahashi Misa,
Goshima Naoki,
Kawakami Shigeki,
Irifune Kohei,
Morikawa Hiromichi
Publication year - 2001
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.2001.2641035.x
Subject(s) - biology , transgene , transformation (genetics) , microbiology and biotechnology , scaffold/matrix attachment region , concatemer , dna , gene , nucleic acid sequence , genetics , expression cassette , genomic dna , regulatory sequence , genome , gene expression , recombinant dna , chromatin remodeling , vector (molecular biology)
Summary A 12.5‐kb DNA fragment with junction regions between the transgene and genomic DNA was cloned from a transgenic tobacco cell line obtained by microprojectile bombardment of plasmid pCaMVNEO. Nucleotide sequence analysis of the fragment (DDBJ accession no. D84238) showed that it carried a 7.7‐kb core sequence (concatemer of a complete pCaMVNEO and a partial pCaMVNEO) and two identical 1.3‐kb junction sequences that flanked both the 5′ and 3′ ends of the core sequence and had inverted orientations. These sequences had topoisomerase II (Topo II) cleavage sites and adenine and thimine‐rich sequences known to be specific to nuclear scaffold‐attachment regions (SARs). An in vitro binding assay showed that a 507‐bp fragment (designated TJ1) from the 1.3‐kb sequence had the ability to bind to nuclear scaffold preparations of cultured tobacco cells, confirmation that the 1.3‐kb sequence is an SAR. Insertion of TJ1at the 5′ and 3′ sides of the expression cassette for the npt II gene increased transformant yields 5‐ to 10‐fold and the NPT II enzyme activity per copy of the gene 5‐fold. TJ1enhances the integration or expression of the transgene, or both. Clearly, TJ1is very useful for producing transgenic plants. This is the first report on an SAR‐like sequence that is located in the transgene locus and enhances transformation efficiency in eukaryotic cells. The possible role of TJ1‐SAR in the molecular evolution of plant genome is discussed.