Tissue-, period-and site-specificity of somatic DNA recombination in the genomic region, BC-1

The nuclear circular DNA population has been analyzed in mouse brain cells. Thebrain is active in producing extrachromosomal nuclear circular DNA during theembryonic and newborn neonatal stage. One circular DNA, BC-1,1 was cloned from amouse embryonic circular DNA library. The genomic region containing the BC-1 DNAsequence was shown to undergo somatic DNA recombination yielding a DNA deletionand circular DNA in mouse embryonic brain. The genomic BC-1 region is also active inDNA recombination in non-brain organ tissue such as the ocular lens and spleen.Although the BC-1 region contains an evolutionally conservative DNA sequencehomologous to the DNA sequence on human chromosome 3, the BC-1 does not containany conventional exon and intron structure. The physiological significance and themolecular mechanism of the BC-1 DNA recombination and the BC-1 RNA expressionare not clear. In this study, the DNA sequence surrounding the BC-1 region and BC-1RNA expression are further analyzed as a first step in order to explain for the mechanismof the somatic BC-1 DNA recombinational events.