Aberrant splicing at the CAG repeat tract.

A. Amplification of GFP transcripts from induced GFP(CAG)₈₉ cells by RT-PCR. B. Splice junctions in normal and aberrantly spliced GFP mRNA. The lower band in A corresponds to correctly spliced GFP mRNA, with sequences around the splice sites indicated above the gene. The upper band in A corresponds to aberrantly spliced mRNA that included the CAG repeat as an extra exon. Splice sites at the ends of the CAG exon are indicated below the gene. In all cases, upper case letters were retained in the spliced product and lower case letter were eliminated. An in-frame stop codon is highlighted in bold. The Not1 site that was used to clone the CAG repeat tract, along with its 129 bp of flanking sequences, is indicated as N. C. Northern blot analysis of GFP transcripts in induced cell lines with different lengths of CAG repeat tracts. Numbers above the lanes indicate the length of the CAG repeat tract. The lane labeled “0” is from GFP(CAG)₀ cells. The upper panel shows the Northern blot, using a hybridization probe made from the full-length EGFP gene. The lower panel shows rRNA bands present in the ethidium bromide-stained gel prior to transfer for blot analysis.