Indeed, this staining largely associates with the interbands, representative of less dense chromatin. One role of the short isoform may be during central nervous system formation during embryogenesis, in controlling glial and neuronal patterning. Analysis of the dATRX3 mutation that removes the long isoform shows no visible phenotype, aside from reduced viability of the flies. Studies of the chromatin structure in these mutants have failed to show any difference in the nucleosome spacing as judged by micrococcal nuclease digestion. This could simply be a consequence of the limitations of this assay or alternatively could suggest a different role in higher order structure formation, or redundancy with other chromatin remodelling factors such as dMi-2. In order to form a condensed, heterochromatic structure, nucleosome positions must be optimised such that the relative orientations of two nucleosomes are consistent along the fibre. This would allow a regular, ordered structure to form, essential for the formation of a compact fibre and subsequent further folding into a higher order structure such as heterochromatin. Drosophila ACF has been shown to act to alter nucleosome repeat lengths both in vitro and in vivo, suggesting a role in ����shuffling���� of nucleosome positions to generate a more uniform array. One role of the dATRX remodelling factor may be to Darunavir achieve this. A second mechanism may be by inducing twist, which would aid or antagonise compaction of the chromatin fibre depending on its direction. We suggest that chromatin remodellers are the end effectors of histone modifications. Consistent with this view, many remodelling complexes contain components that recognise specific modification states of histone tails. For instance, the SANT domain of dISWI may bind to unmodified tails, while one of the PHD domains from human Mi-2 binds preferentially to trimethylated lysine 36 of histone H3, which marks the end of active transcription units. ATRX may be Fosinopril Sodium recruited by its interaction with HP-1 or MeCP2 to heterochromatin, or the PHD domain in the human protein may play a role in methylated histone binding.