HSPB7 is a SC35 speckle resident small heat shock protein.
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.


CONCLUSIONS
Our data suggest a non-chaperone-like role of HSPB7 at SC35 speckles.


CONCLUSIONS
The functional divergence between HSPB members seems larger than previously expected and also includes non-canonical members lacking classical chaperone-like functions.
Vos
Michel J
MJ
Department of Cell Biology, Section of Radiation and Stress Cell Biology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Kanon
Bart
B
Kampinga
Harm H
HH
D002460:Cell Line; D020541:Coiled Bodies / Q000378:metabolism; D005260:Female; D055551:HSP27 Heat-Shock Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006367:HeLa Cells; D006360:Heat-Shock Proteins; D050888:Heat-Shock Proteins, Small / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D018832:Molecular Chaperones; D011247:Pregnancy; D011489:Protein Denaturation; D017510:Protein Folding; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D014018:Tissue Distribution; D015533:Transcriptional Activation
D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; D050888:Heat-Shock Proteins, Small; D018832:Molecular Chaperones; D012333:RNA, Messenger; D011994:Recombinant Proteins