The Drosophila homolog of the human AF10 is an HP1-interacting suppressor of position effect variegation

In chromosomal rearrangements of acute myeloid leukaemia patients the mixed lineage leukaemia (MLL) gene, a human homolog of the Drosophila gene trithorax, is frequently fused to AF10. Here we describe the identification and a functional characterization of the Drosophila homolog dAF10. We show that dAF10 functions in heterochromatin-dependent genomic silencing of position effect variegation, a phenomenon associated with chromosomal rearrangements that cause mosaic expression of euchromatic genes when relocated next to heterochromatin. We also demonstrate that dAF10 can associate with the heterochromatin protein 1 (HP1) in vitro and in vivo. The results indicate that dAF10 is an HP1-interacting component of the heterochromatin-dependent gene silencing pathway, which either contributes to the stability of the heterochromatin complex or to its function.