Document Detail

Cell number-dependent regulation of Hsp70B' expression: evidence of an extracellular regulator.
MedLine Citation:
PMID:  17044073     Owner:  NLM     Status:  MEDLINE    
Hsp70B' is a unique member of the human Hsp70 family of chaperones about which information is scarce. Unlike the major inducible Hsp72 protein, Hsp70B' is strictly inducible having little or no basal expression levels in most cells. We observed that Hsp70B' appears transiently in response to heat stress whereas Hsp72 levels persist for many days. Also, Hsp70B' is optimally induced when cell numbers are low, whereas Hsp72 levels are greatest at higher cell number. Hsp70B' promoter activation was measured by flow cytometry using an Hsp70B' promoter-driven GFP construct. In heat stressed cells, promoter activation is cell number independent over a broad range. However, when cell number increases beyond a certain population size, cells are less stress inducible for Hsp70B' and induction becomes highly cell number-dependent. Cell number differences in Hsp70 activation cannot be explained by changes in Hsf-1 DNA-binding activity or hyperphosphorylation. Cells with few or no cell matrix attachments (laminin-coated and low attachment plates, respectively) appear to be more sensitive to cell number-dependent inhibition. Medium conditioned by the low cell number (LCN) populations supports increased Hsp70B' promoter activation in high cell number (HCN) cultures. Likewise, medium conditioned in HCN culture conditions causes decreased activation of Hsp70B' promoter in LCN cultures. As HCN-conditioned medium has all the components necessary for cell growth, two possibilities for the activation of Hsp70B' gene expression exist: an inhibitory component that accumulates in culture medium at HCN, or an activator that accumulates at LCN.
Emily J Noonan; Robert F Place; Reza J Rasoulpour; Charles Giardina; Lawrence E Hightower
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Journal of cellular physiology     Volume:  210     ISSN:  0021-9541     ISO Abbreviation:  J. Cell. Physiol.     Publication Date:  2007 Jan 
Date Detail:
Created Date:  2006-11-06     Completed Date:  2007-02-02     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0050222     Medline TA:  J Cell Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  201-11     Citation Subset:  IM    
Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, USA.
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MeSH Terms
Cell Communication
Cell Count
Cell Nucleus / metabolism
Cell Proliferation* / drug effects
Colonic Neoplasms / metabolism*,  pathology
Culture Media, Conditioned / pharmacology
Cytosol / metabolism
DNA-Binding Proteins / metabolism
Genes, Reporter
Green Fluorescent Proteins
HSP27 Heat-Shock Proteins
HSP70 Heat-Shock Proteins / genetics,  metabolism*
HSP72 Heat-Shock Proteins / metabolism
HT29 Cells
Heat-Shock Proteins / metabolism
Hot Temperature
Laminin / metabolism
Neoplasm Proteins / metabolism
Promoter Regions, Genetic / drug effects,  genetics
Proteasome Endopeptidase Complex / metabolism
Protein Binding
Time Factors
Transcription Factors / metabolism
Transcription, Genetic*
Grant Support
Reg. No./Substance:
0/Culture Media, Conditioned; 0/DNA-Binding Proteins; 0/HSP27 Heat-Shock Proteins; 0/HSP70 Heat-Shock Proteins; 0/HSP72 Heat-Shock Proteins; 0/HSPA7 protein, human; 0/HSPB1 protein, human; 0/Heat-Shock Proteins; 0/Laminin; 0/Neoplasm Proteins; 0/Transcription Factors; 0/heat shock transcription factor; 147336-22-9/Green Fluorescent Proteins; EC Endopeptidase Complex

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