How to get out: ssRNA enveloped viruses and membrane fission

Enveloped viruses acquire their membrane from the host cell and accordingly need to separate their envelope from cellular membranes via membrane fission. Although some of the enveloped viruses recruit the endosomal sorting complex required for transport (ESCRT) to catalyze the final fission reaction, many enveloped viruses seem to bud in an ESCRT-independent manner. Here we describe the principles that govern membrane fission reactions in general and review progress in the understanding of ESCRT-mediated membrane fission. We relate ESCRT function to budding of single stranded RNA viruses and discuss alternative ways to mediate membrane fission that may govern ESCRT-independent budding.