PMID- 10413683
OWN - NLM
STAT- MEDLINE
DCOM- 19991028
LR  - 20191210
IS  - 0021-9533 (Print)
IS  - 0021-9533 (Linking)
VI  - 112 ( Pt 16)
DP  - 1999 Aug
TI  - Human heat shock factor 1 is predominantly a nuclear protein before and after
      heat stress.
PG  - 2765-74
AB  - The induction of the heat shock genes in eukaryotes by heat and other forms of
      stress is mediated by a transcription factor known as heat shock factor 1 (HSF1).
      HSF1 is present in unstressed metazoan cells as a monomer with low affinity for
      DNA, and upon exposure to stress it is converted to an 'active' homotrimer that
      binds the promoters of heat shock genes with high affinity and induces their
      transcription. The conversion of HSF1 to its active form is hypothesized to be a 
      multistep process involving physical changes in the HSF1 molecule and the
      possible translocation of HSF1 from the cytoplasm to the nucleus. While all
      studies to date have found active HSF1 to be a nuclear protein, there have been
      conflicting reports on whether the inactive form of HSF is predominantly a
      cytoplasmic or nuclear protein. In this study, we have made antibodies against
      human HSF1 and have reexamined its localization in unstressed and heat-shocked
      human HeLa and A549 cells, and in green monkey Vero cells. Biochemical
      fractionation of heat-shocked HeLa cells followed by western blot analysis showed
      that HSF1 was mostly found in the nuclear fraction. In extracts made from
      unshocked cells, HSF1 was predominantly found in the cytoplasmic fraction using
      one fractionation procedure, but was distributed approximately equally between
      the cytoplasmic and nuclear fractions when a different procedure was used.
      Immunofluorescence microscopy revealed that HSF1 was predominantly a nuclear
      protein in both heat shocked and unstressed cells. Quantification of HSF1
      staining showed that approximately 80% of HSF1 was present in the nucleus both
      before and after heat stress. These results suggest that HSF1 is predominantly a 
      nuclear protein prior to being exposed to stress, but has low affinity for the
      nucleus and is easily extracted using most biochemical fractionation procedures. 
      These results also imply that HSF1 translocation is probably not part of the
      multistep process in HSF1 activation for many cell types.
FAU - Mercier, P A
AU  - Mercier PA
AD  - Department of Zoology, University of Toronto, Mississauga, Ontario, Canada L5L
      1C6.
FAU - Winegarden, N A
AU  - Winegarden NA
FAU - Westwood, J T
AU  - Westwood JT
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - England
TA  - J Cell Sci
JT  - Journal of cell science
JID - 0052457
RN  - 0 (Antibodies)
RN  - 0 (DNA-Binding Proteins)
RN  - 0 (Fluorescent Dyes)
RN  - 0 (HSF1 protein, human)
RN  - 0 (Heat Shock Transcription Factors)
RN  - 0 (Heat-Shock Proteins)
RN  - 0 (Transcription Factors)
RN  - I223NX31W9 (Fluorescein-5-isothiocyanate)
SB  - IM
MH  - Animals
MH  - Antibodies
MH  - Cell Fractionation
MH  - Cell Nucleus/chemistry/*metabolism
MH  - Chlorocebus aethiops
MH  - DNA-Binding Proteins/analysis/immunology/*metabolism
MH  - Fluorescein-5-isothiocyanate
MH  - Fluorescent Antibody Technique, Indirect
MH  - Fluorescent Dyes
MH  - HeLa Cells
MH  - Heat Shock Transcription Factors
MH  - Heat-Shock Proteins/analysis/immunology/*metabolism
MH  - Heat-Shock Response/*physiology
MH  - Humans
MH  - Temperature
MH  - Transcription Factors
MH  - Vero Cells
EDAT- 1999/07/22 00:00
MHDA- 1999/07/22 00:01
CRDT- 1999/07/22 00:00
PHST- 1999/07/22 00:00 [pubmed]
PHST- 1999/07/22 00:01 [medline]
PHST- 1999/07/22 00:00 [entrez]
PST - ppublish
SO  - J Cell Sci. 1999 Aug;112 ( Pt 16):2765-74.