Prothymosin α is a component of a linker histone chaperone

Linker histone H1 binds with high affinity to naked and nucleosomal DNA in vitro but is rapidly exchanged between chromatin sites in vivo suggesting the involvement of one or more linker histone chaperones. Using permeabilized cells, we demonstrate that the small acidic protein prothymosin alpha (ProT alpha) can facilitate H1 displacement from and deposition onto the native chromatin template. Depletion of ProT alpha levels in vivo by siRNA-mediated mRNA degradation resulted in a decreased rate of exchange of linker histones as assayed by photobleaching techniques. These results indicate that ProT alpha is a component of a linker histone chaperone. (C) 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.