The conserved band-interband pattern is thought to reflect the looped-domain 
organization of insect polytene chromosomes. Previously, we have shown that the 
chromodomain protein Chriz and the zinc-finger protein Z4 are essentially 
required for the maintenance of polytene chromosome structure. Here we show that 
both proteins form a complex that recruits the JIL-1 kinase to polytene 
chromosomes, enabling local H3S10 phosphorylation of interband nucleosomal 
histones. Interband targeting domains were identified at the N-terminal regions 
of Chriz and Z4, and our data suggest partial cooperation of the complex with 
the BEAF boundary element protein in polytene and diploid cells. Reducing the 
core component Chriz by RNAi results in destabilization of the complex and a 
strong reduction of interband-specific histone H3S10 phosphorylation.