Cytoplasmic interaction of the tumour suppressor protein hSNF5 with dynamin-2 controls endocytosis.

Human SNF5 (hSNF5; INI1, SMARCB1 or BAF47) is a component of the human SWI/SNF chromatin remodelling complex and a tumour suppressor mutated in rhabdoid tumours. It also associates with the integrase of the human immunodeficiency virus (HIV)-1. We show by fluorescence loss in photobleaching that hSNF5 is constantly shuttling between the nucleus and the cytoplasm, raising the question of what the role of hSNF5 is in the cytoplasm. Here, we demonstrate that hSNF5 directly interacts with the GTPase dynamin-2 (DNM2) in the cytoplasm. DNM2 is a large GTPase involved in endocytosis and vesicle dynamics, which has been related to HIV-1 internalization. We show that hSNF5 colocalizes with DNM2 in endocytic vesicles. Depletion of hSNF5, but not of other components of the SWI/SNF complex, destabilizes DNM2 and impairs DNM2-dependent endocytosis. Furthermore, we show that hSNF5 inhibits assembly-stimulated DNM2 GTPase activity but not basal GTPase activity in vitro. Altogether, these results indicate that hSNF5 affects both the stability and the activity of DNM2, uncovering an unexpected role of hSNF5 in modulating endocytosis, and open new perspectives in understanding the role of hSNF5 in tumour genesis.