Fig. 2.

fh20 is a hypomorphic cryptic splice allele of foggy/spt5. (A) Genomic sequence analysis indicates the fh20 allele is a C-T transition corresponding to position 1904 of the spt5 mRNA. (B) This base change (red arrow) results in the creation of an AGGT consensus splice donor sequence (underlined), and the eight base region including the change (box in fh20) matches eight bases around the endogenous splice donor (boxes in wt and fh20) for exon 15 (shaded green). Sequence analysis of fh20^-/- cDNA shows a double trace indicating that correctly and incorrectly spliced mRNA transcripts are present in the same fh20 mutant. Thus the fh20 allele is a hypomorph. (C) The misspliced mRNA results in a frameshift, and the protein terminates at amino acid (∼676), prior to the fourth KOW RNA pol II binding motif.