P{PZ} inserted into the largest intron of psq provides a splice acceptor site and termination signal, causing the psq initiated transcript to be spliced in the P{PZ} element, then truncated. Fusion gene includes 5' psq transcript through to and including the BTB domain, and 3' l(3)87Df sequences.

Insertion of P{PZ} into the largest intron of psq leads to the production of a spliced transcript encoding 105 amino acids from the N-terminus of psq fused to 63 amino acids from l(3)87Df.