HSPB7 is a SC35 speckle resident small heat shock protein.
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Vos MJ, Kanon B, Kampinga HH
HSPB7 is a SC35 speckle resident small heat shock protein.
Biochim Biophys Acta. 2009 Aug;1793(8):1343-53. doi: 10.1016/j.bbamcr.2009.05.005. Epub 2009 May 21.
- PubMed ID
- 19464326 [ View in PubMed]
- Abstract
BACKGROUND: The HSPB family is one of the more diverse families within the group of HSP families. Some members have chaperone-like activities and/or play a role in cytoskeletal stabilization. Some members also show a dynamic, stress-induced translocation to SC35 splicing speckles. If and how these features are interrelated and if they are shared by all members are yet unknown. METHODS: Tissue expression data and interaction and co-regulated gene expression data of the human HSPB members was analyzed using bioinformatics. Using a gene expression library, sub-cellular distribution of the diverse members was analyzed by confocal microscopy. Chaperone activity was measured using a cellular luciferase refolding assay. RESULTS: Online databases did not accurately predict the sub-cellular distribution of all the HSPB members. A novel and non-predicted finding was that HSPB7 constitutively localized to SC35 splicing speckles, driven by its N-terminus. Unlike HSPB1 and HSPB5, that chaperoned heat unfolded substrates and kept them folding competent, HSPB7 did not support refolding. CONCLUSION: Our data suggest a non-chaperone-like role of HSPB7 at SC35 speckles. GENERAL SIGNIFICANCE: The functional divergence between HSPB members seems larger than previously expected and also includes non-canonical members lacking classical chaperone-like functions.