Structure and mechanism of the Ino80 chromatin remodelling complex

Compaction of the genome into chromatin helps to protect the genetic material but also causes problems in regard to access for essential processes such as transcription, replication and repair. Chromatin remodelling complexes alter the state of chromatin through a number of processes that includes chemical modifications of nucleosomes and sliding their position on DNA. Nucleosome sliding is catalysed by a number of protein complexes, one of which is the multi-subunit INO80 complex. INO80 contains an ATP-dependent translocase motor, that is common to all nucleosome sliders, but also a variety of other subunits, most of which have unknown roles. Furthermore, not only does it require two INO80 complexes interacting with a single nucleosome to promote sliding, but the complex also has an ability to “sense” the presence of other nucleosomes to space them evenly on DNA indicating interactions with multiple nucleosomes. The mechanism for this process is poorly understood, particularly at a molecular and structural level. INO80 is highly regulated in several distinct ways, including chemical modifications, small molecule effectors and subunit interactions but none of these are well understood. Finally, how the various subunits, many of which are ATPases in their own right, contribute to INO80 activities is also unclear.