Open reading frame encoding 'a' isoform of CrebB, expressed from an Hsp70 promoter.

Heat-shock promoter sequences drive expression of CrebB coding sequences corresponding to the CrebB-a isoform with a sequence rearrangement that results in a premature stop codon (see FBrf0180428 for details). An in-frame Met codon (ATG2) is present downstream of the premature stop codon, potentially allowing for translate to initiate, or reinitiate at this 'ATG2' codon. Western analysis using an antibody raised against residue downstream of ATG2 suggests that this transgene does produce a protein, whose mobility is consistent with translation initiation at ATG2. This protein is equivalent to a short CrebB isoform that is weakly expressed in flies.

The P{hs-dCREB2-a} transgene originally described in FBrf0080505 has been sequenced. It has been found to contain 4 differences relative to the sequence of the 'CREB activator' isoform described in FBrf0080505; a G to A base substitution results in a G36S amino acid substitution, the GGT triplet encoding G is missing at amino acid position 47, a T to C base substitution has no effect on Tyr residue 353, and most significantly, a single G nucleotide is missing in amino acid position 38, resulting in a frameshift that leads to a stop codon at position 79.