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Mol. Cell. Biol., Oct 1995, 5288-5293, Vol 15, No. 10
ML Goodson, OK Park-Sarge and KD Sarge
Heat shock factor 2 (HSF2) functions as a transcriptional regulator of heat
shock protein gene expression in mammalian cells undergoing processes of
differentiation and development. Our previous studies demonstrated high
regulated expression and unusual constitutive DNA- binding activity of the
HSF2 protein in mouse testes, suggesting that HSF2 functions to regulate
heat shock protein gene expression in spermatogenic cells. The purpose of
this study was to test whether HSF2 regulation in testes is associated with
alterations in the HSF2 polypeptide expressed in testes relative to other
mouse tissues. Our results show that mouse cells express not one but two
distinct HSF2 proteins and that the levels of these HSF2 isoforms are
regulated in a tissue-dependent manner. The testes express predominantly
the 71-kDa HSF2-alpha isoform, while the heart and brain express primarily
the 69- kDa HSF2-beta isoform. These isoforms are generated by alternative
splicing of HSF2 pre-mRNA, which results in the inclusion of an 18-
amino-acid coding sequence in the HSF2-alpha mRNA that is skipped in the
HSF2-beta mRNA. HSF2 alternative splicing is also developmentally
regulated, as our results reveal a switch in expression from the HSF2- beta
mRNA isoform to the HSF2-alpha isoform during testis postnatal
developmental. Transfection analysis shows that the HSF2-alpha protein, the
predominant isoform expressed in testis cells, is a more potent
transcriptional activator than the HSF2-beta isoform. These results reveal
a new mechanism for the control of HSF2 function in mammalian cells, in
which regulated alternative splicing is used to modulate HSF2
transcriptional activity in a tissue-dependent manner.
Copyright © 1995, American Society for Microbiology
Tissue-dependent expression of heat shock factor 2 isoforms with distinct transcriptional activities
Department of Biochemistry, Chandler Medical Center, University of Kentucky, Lexington 40536-0084, USA.
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