May play a role in the process of early and late gene activation, or possibly in RNA processing, for a defined set of developmentally regulated loci. It is associated with the active ecdysone-regulated loci on polytene chromosomes, and on some heat shock-induced puffs. Its distribution pattern follows the changes of puffing patterns in the developmental program, or following heat shock. Expressed both maternally and zygotically, zygotic expression is at a low and constant level thereafter. Intron retention.