R. Ohki et al., PREFERENCE OF THE RECOMBINATION SITES INVOLVED IN THE FORMATION OF EXTRACHROMOSOMAL COPIES OF THE HUMAN ALPHOID SAU3A REPEAT FAMILY, Nucleic acids research, 23(24), 1995, pp. 4971-4977
The human alphoid Sau3A repetitive family DNA is one of the DNA specie
s that are actively amplified to form extrachromosomal circular DNA in
several cell lines. The circularization takes place between two of th
e five similar to 170 bp subunits with an average of 73.1% homology as
well as between identical subunits, To investigate the nature of the
recombination reaction, we cloned and analyzed the subunits containing
recombination junctions. Analysis of a total of 68 junctions revealed
that recombination had occurred preferentially at four positions 10-2
5 (A), 40-50 (B), 85-90 (C) and 135-160 (D) in the 170 bp subunit stru
cture, Two regions (B and C) were overlapped with the regions with hig
her homology between subunits, while other two regions (A and D) canno
t be explained solely by the regional homology between the subunits, T
hese regions were located at both junctions of the nucleosomal and the
linker region, and overlapped with the binding motifs for a protein a
nd CENP-B, Approximately 90% of the recombination occurred between the
subunits located next but one (+/- 2 shift), although the frequency o
f recombination between the adjoining subunits (+/- 1 shift) was simil
ar to 10%.