Heat shock protein (HSP) 27 is one of the small HSPs. Like other small heat shock proteins, HSP27 is regulated at both the transcriptional and posttranslational levels . In response to stress, the expression level of HSP27 increases several-fold to confer cellular resistance to the adverse environmental change.

HSP27 is phosphorylated at Ser15, Ser78 and Ser82 by MAPKAP kinase 2 as a result of the activation of the p38 MAP kinase pathway . Phosphorylation of HSP27 causes a change in its tertiary structure, which shifts from large homotypic multimers to dimers and monomers . It has been shown that phosphorylation and increased concentration of HSP27 modulates actin polymerization and reorganization .