The RNA chaperon activity of the human La protein (LARP3)

Single-stranded RNA molecules fold intensively into secondary and tertiary structures and are often trapped in non-functional configurations. To adapt a functional configuration, structural changes have to be achieved. RNA helicases and RNA chaperones are proteins able to assist those structural rearrangements in an ATP-dependent or ATP-independent manner, respectively. The cancer-associated RNA-binding protein La (LARP3) is an RNA chaperone involved in various aspects of the RNA metabolism. Recently the RNA chaperone domain within the human La protein has been mapped and demonstrated that its activity is required to stimulate cyclin D1-internal ribosome entry site (IRES)-dependent protein synthesis. Furthermore, it has been shown that the La protein can be phosphorylated by serine/threonine kinase AKT in vitro. Taken together, we suggest a model in which the RNA chaperone La stimulates translation of specific target mRNAs by assisting structural changes in their translation start site surrounding RNA region.