THE FIRST EXON OF THE RAT ALDOLASE-C GENE IS ESSENTIAL FOR RESTORING THE CHROMATIN STRUCTURE IN TRANSGENIC MICE

A 13-kb fragment of the rat aldolase C gene contains sufficient inform ation for gene expression, Transgenic mice carrying the 13-kb fragment showed restoration of chromatin structure and tissue-specific, copy n umber-dependent expression. To localize the regulatory elements respon sible for restoring chromatin structure, several mutated constructs we re used to produce transgenic mice. Three activities were examined: re creation of DNase hypersensitive sites, restoration of methylation sta tus, and copy number-dependent expression, Deletions of the 3'-flankin g region did not affect those activities. Deletion of seven introns af fected the mRNA levels but not the restoration of the chromatin struct ure. The insertion of the LacZ gene into the first exon of the transge ne interfered with both the restoration of the chromatin structure and the copy number-dependent expression in transgenic mice. DNase I foot printing assays revealed that brain-specific factors bind to the seque nce disrupted by the LacZ insertion, These results suggest that the se quence in the first exon is essential for restoring the chromatin stru cture of the rat aldolase C gene.