Nucleic acids, compositions and methods for excision of target nucleic acids
A target nucleic acid, nucleic acid technology, applied in the field of nucleic acid, composition and method for excising target nucleic acid, and can solve the problems of low frequency of excision events and the like
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Embodiment 1
[0125] 6.1 Example 1: Construction of x-marker constructs
[0126] The compositions and methods described herein were used to prepare and identify a series of excisable selectable markers for Saccharomyces cerevisiae, referred to herein as "x-markers". The first generation of labeling uses I-SceI endonuclease, and the parameters of the DNA constructs detected are given in figure 1 , parameters included: (1) different lengths of the forward repeat flanks of the endonuclease sites and (2) a comparison of one and two endonuclease sites. The second generation of markers applies the results of the first generation of assays, which broaden the application of the I-SceI endonuclease. The third-generation x-label has proven effective and can be extended to other endonucleases listed in Table 1 below.
[0127] Table 1: Endonuclease recognition and cleavage sites.
[0128]
[0129] Reagents used in the experiments are described below and restriction enzymes were from New England B...
Embodiment 2
[0191] 6.2 Example 2: Excision of chromosomal DNA selectable markers
[0192] This example demonstrates that the x-marker construct described in Example 1 is capable of mediating excision of the selectable marker from the chromosomal DNA of the host cell. As described below, the constructs are transformed into cells, cells are plated into media selective for the x-marker, and correct integration is confirmed by colony PCR; such strains are treated in the same manner as any other prepared using standard markers The strains are the same, and the x mark can exist stably. Third, when excision of the x-marker is desired, transform the strain with a single-copy (CEN.ARS) plasmid containing its own marker and a homing endonuclease gene expression construct, as described in the following sections. Strains were tested for loss of the x-marker after several generations of selection for the presence of the plasmid and growth under conditions that induced expression of the homing endon...
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